Re: How do you measure a car antenna?
Yes. There is a benefit to filtering in the physical world, such as a tunable pre-selector or fixed band pass filter to reduce incoming RF that is not within the frequencies of interest. I agree that the traditional car radio whip antenna is a voltage probe. Antenna people might say it is such a small physical size in relation to the wavelength that it can not be much of anything else.
The earlier comment about many VNAs being SDRs with essentially wide band "chip" level components connected to an antenna really made me think.
You can really see how attractive this is to the marketplace, but considering congestion in the RF spectrum and the presence of strong undesired signals this is not wise. From a spectrum management view the goal is maximum use of desirable spectrum, and this usually means packing 'em in, with minimal frequency separation. Then on the receive end everything goes to SDRs with wide open front ends.
I work in broadcasting in the US. Local FM channel spacing is effectively 800 KHz. That means a physical filter, or components that remain linear with equal or greater local signals on the fourth-adjacent channel. (800 KHz away).
In my Nano VNA usage, it is working for me with trap between the Nano VNA and a large antenna. There is about 25 volts of RF at a nearby frequency on the antenna. The series LC parallel tuned circuit reduces this voltage to under 100 millivolts.
It appears more expensive VNAs have greater maximum front end signal level specifications and dynamic range. This is helpful, but we still have the reality of strong signals present that will not go away unless other users cooperate.
Until we go to high GHz use exclusively or build very robust components, it appears large scale physical things remain useful.
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Re: nano VNA-H will not connect via USB to control apps on Win10 - help please
Hi Stan
I have tried everything possible to get this unit to connect to a PC. I did have one computer which I had not connected it to and it wouldn't work with that one either. I can only conclude that the USB comms chip in the unit is defective.
The eBay returns window on this unit closed on 1 July. That's how long I have been messing around with this thing trying to make it work. I have contacted the seller moralstreasure-006 to see if they will make good.
Thanks
-Brian
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Re: How do you measure a car antenna?
Have you tried to add a low pas or notch filter?
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On 8/27/2023 1:22 PM, W0LEV wrote: I don't like to be the bearer of bad news, but the dealership has no idea
what RFI is. They know the words and there is a problem with some Jeep
models, but that's as far as they go. Experience follows:
While somewhat of an esoteric problem with RFI: the "Water Hole"
surrounding 1420.405751 MHz. This is the emission line of celestial and
deep space hydrogen designated by HI. The Water Hole is protected spectrum
by international agreement, including the US. Well,......., read on.
We have a 2018 Jeep JL Rubicon. It, of course, includes the capability of
serving as a hotspot for the internet and making cell phone calls. As
such, it contains a cell modem as part of the electronics behind the video
display in the dash. That modem operates at nominally 700 MHz (I've easily
detected its fundamental frequency output on the spectrum analyzer) . The
second harmonic screams out of the assembly and blankets the hydrogen line
such that I can not do radio astronomy on that frequency. It ceases
"looking for mommie" - finding a cell tower as we have no cell coverage at
home - after sitting untraveled for 3 or 4 days. Does it track my
travels? Absolutely yes, but that's a different problem.
I have four times contacted the local dealership where we bought the
vehicle. They have absolutely no inkling of what I'm talking about other
than recognizing the term "Radio Frequency Interference". I've sent Jeep
in Toledo - their engineering department - three letters documenting,
screen grabs, the interference both as captured on the spectrum analyzer of
the second harmonic of the cell modem and in the time domain from my
receiver as captured on the laptop at 1420 MHz (after some downconversion
and detection). There has been absolutely no response from them, either,
other than a form email "thanking me for my interest in Jeep".........which
we already own. Thanks, but no thanks!
Frustrated......? Yes.......! There are instructions online on disabling
the cell modem, but since we camp off-grid in many...many locations which
do not have any cell coverage or amateur repeaters, I'm reluctant to do
so. In addition, it involves literally taking the whole dash apart which
I'm not into attempting.
All I can communicate is, "good luck"........and, there really is no such
thing as "luck". YMMV......?
Dave - W?LEV
On Sat, Aug 26, 2023 at 11:49?PM Glenn Little <glennmaillist@...>
wrote:
Take it back to the dealer and insist that they fix the problem.
The problem is poorly designed and implemented inverters for the battery
and electronics.
It probably does not meet part 15 FCC rules for unintentional radiators.
Glenn
On 8/26/2023 12:59 PM, Donald S Brant Jr wrote:
If you are describing a problem with AM reception, it could be EMI from all of the inverters, etc. in the car, interfering with reception, rather
than an antenna issue. I had heard that car makers were trying to move
away from having AM to side step this issue. 73, Don N2VGU
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIVwb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
Re: How do you measure a car antenna?
I live in North Central Florida. You can hear the traffic lights change on AM car radios, ell over a mile from those? crap LED traffic lights. The olny time I ge decent AM reception at home is after a hurricane when the power is out for the region.
toggle quoted message
Show quoted text
On 8/26/2023 12:59 PM, Donald S Brant Jr wrote: If you are describing a problem with AM reception, it could be EMI from all of the inverters, etc. in the car, interfering with reception, rather than an antenna issue. I had heard that car makers were trying to move away from having AM to side step this issue. 73, Don N2VGU
|
Re: How do you measure a car antenna?
Old car radios had a tuned RF input, and an RF amplifier. I't's hard to beat a '63 to late '70's? Delco AM car radio. They used a variable inductor tuning system, with very good tracking between stages. Later designs eliminated the tuned front? end which both lowers sensitivity and noise rejection. This started with Japanese imports in the early '70s. A factory radio was hundreds of dollars, but the crap design import was $20.? I serviced hundreds, if not thousands of car radios in the early to mid '70s. Ford and Chrysler radios were a joke, compared to Delco. Ford even used Delco radios in their high end Lincolns. Ford owned Philco, but they also used Bendix and Motorola radios. Chrysler used pink plastic circuit boards that would melt when you tried to repair them.
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On 8/26/2023 10:22 PM, fbray@... wrote: At the risk of being slightly OT, there are several reasons that AM radios are disappearing. One is the EMI problem caused by various vehicle charging and propulsion systems. The EMI issue is a discussion topic on forums frequented by public safety and commercial two-way radio techs.
European car makers have dropped AM because it has been supplanted by DAB and AM stations are shutting down there, leaving little to listen to. Major US car makers disclaim any intention to abandon AM but we'll have to wait and see. In major US metro areas some of the AM stations are now simulcasting on FM so that they don't lose their audience.
Many of us have noted that the AM radios in older cars with traditional external metal rod antennas work better than the in the glass antennas.
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Re: updated and calibrated nanovna h4 yields incorrect swr readings
I recently ran across: "RTL-SDR Blog SMA Male to ..." on Amazon for $26.95. Ten different jumper cables with SMA Male on one end and an assortment of popular connector types, both Male and Female on the other. All connectors intermated smoothly with old school silver plated ones in my collection.
|
Re: How do you measure a car antenna?
An AM radio antenna on a car is actually a voltage probe. I used to talk with Delco car radio engineers many decades ago at their annual schoolswhere they indroduced new designs to techs who did warranty work. The coax is 93 ohhms, on older radios, to minimze the capacatnce per foot, but a lot of cheap antennas use smaller, 50 ohm coax.
31" was chosen for FM car radio antennas to be in the middle of the 88 to 108 MHz range.
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On 8/26/2023 1:31 PM, Ben Cranston via groups.io wrote: To further W0LEV¡¯s point, a good friend of mine works for that manufacturer, specifically on that truck, and said that the EMI from the PWM controllers in powertrain and battery management system was a large consideration for the decision to disable AM on the radio stack. Additionally the radios are now SDR based and have highly sensitive basically wide open RF front ends.
My personal experience is that EV manufacturers struggle with EMI, some more than others. I¡¯ve been totally ¡°blown off the air¡± on 10m by a passing Rivian truck. I also know several hams with Tesla vehicles who don¡¯t seem to be plagued by this issue. YMMV...
In my own truck, RAM 1500, a simple aftermarket upgrade has caused a mess of EMI while the engine is running. Who would have thought those performance coil packs would cause so much noise!!!
Anyway, I run the risk of diverting too far from the original post for this thread..
Larry, the central pin ¡°is¡± the resonant element, as compared to the baofeng antenna. The body of the vehicle is the ground plane. So in measuring that antenna, you could unplug it from the radio stack where both conductors are present and use some sort of adapter to make the connection to your nanovna. A measurement of an antenna system should include the transmission line as well, right? By comparison, the baofeng antenna outer shield connects to the radio body and capacitively to your hand to make the ground plane. (or via a tiger tail, but that¡¯s a different discussion)
For a receive only antenna, the impedance match is not super important. These antenna are all compromise antenna and suffer accordingly. The nanovna will provide data points for impedance etc., but its not very helpful for understanding the difference in reception. Furthering what W6PAP said, for receive you are best served by an S-meter or a spectrum analyzer. Heck you might actually be able to quantify potential EMI frequencies with the truck ¡°on¡± verses ¡°off¡± with the analyzer.
For some things to check, verify that the body panel the antenna is mounted on is properly bonded to the rest of the vehicle. Bad ground = poor ground plane. That can change the dynamics of the antenna for certain. Hope that helps and have a great day!
-Ben
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Re: updated and calibrated nanovna h4 yields incorrect swr readings
You can get cheap cables from Ali or Ebay, just buy the
semirigid ones and you should be fine. Hard to mess those up.
I got a few cables like this one
and had 0 issues in the last
3 years since I bought them.
toggle quoted message
Show quoted text
On Thu, 7 Sept 2023 at 04:17, Greg Strickland <greg@...> wrote:
Pasternack made a high quality product when the company I worked for used them about 20 years ago. Good chance it is still a high quality product, at a higher price.
Recently I have ordered components from Newark and Digi-Key. I have a higher level of confidence with them, compared to most of the products that overwhelm Amazon. For components like resistors, capacitors, etc I like to see data sheets and refer to the manufacturers website to see the entire product line. I don't want a generic part. Connectors and intra-series adapters require attention to detail. A high tolerance adapter good to 10 GHZ can be expensive. If you need just 10 MHz a less expensive one or even a generic one might be fine. Cables are a bit more murky. I recently purchased part number 250-086 from Digi-Key. Too soon to comment on durability.
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Pasternack made a high quality product when the company I worked for used them about 20 years ago. Good chance it is still a high quality product, at a higher price.
Recently I have ordered components from Newark and Digi-Key. I have a higher level of confidence with them, compared to most of the products that overwhelm Amazon. For components like resistors, capacitors, etc I like to see data sheets and refer to the manufacturers website to see the entire product line. I don't want a generic part. Connectors and intra-series adapters require attention to detail. A high tolerance adapter good to 10 GHZ can be expensive. If you need just 10 MHz a less expensive one or even a generic one might be fine. Cables are a bit more murky. I recently purchased part number 250-086 from Digi-Key. Too soon to comment on durability.
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Hello Stan,
What model, manufacurer and from what supplier did you obtain the quality sma coax cables?
Thanks.
Al
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Not me, but..... Pasternack is a good supplier, although a bit pricey.
I believe DigiKey also carries their products.
Dave - W?LEV
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023 at 9:42?PM Allan Johnston <adhjohnston@...> wrote: Hello Stan,
What model, manufacurer and from what supplier did you obtain the quality
sma coax cables?
Thanks.
Al
On Wed, Sep 6, 2023, 4:11 PM Stan Dye <standye@...> wrote:
It is not uncommon for the sma-terminated pigtail cables that come with the
nanovna to fail, or to not have been assembled well. Sometimes the shield
is not soldered at the connector, so it passes test at the factory, but
fails the first time you bend it. I ordered a set of better sma pigtail
cables, and haven't had a problem with them.
On Wed, Sep 6, 2023, 2:51 PM Allan Johnston <adhjohnston@...> wrote:
Dave, W0LEV,
It's looking like an intermittent good then bad connection with the
NanoVNA.
The nanovna is connected with the unit's supplied connectors/coax and
additional connector as needed for the antenna.
See attached "nanovna usual bad trace" jpeg that shows the connectors.
The RigExpert connection does not include the small diameter nanovna
coax
cable.
As I set up the RigExpert and NanoVNA for review and photos I
discovered
the flaky intermittent connection in the run of small coax and connectors.
The bad connection is so random that I cannot tell what connector is
the
problem.
More hunting!
Thank you for your response. Your questions helped me discover what is
biting me. At least I know the NanoVNA is working.
If you or anyone else has comments on the trace or the
equipment/coax/connector setup that may help me out then please don't
hesitate to respond.
Al. KA0VIA
On Wed, Sep 6, 2023 at 12:31?PM W0LEV <davearea51a@...> wrote:
How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the
NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you
verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...
wrote:
The Nanovna h4 in use was purchased from R&L Electronics a year or
so
ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The
RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter
antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
--
*Dave - W?LEV*
--
Dave - W?LEV
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Hello Stan,
What model, manufacurer and from what supplier did you obtain the quality
sma coax cables?
Thanks.
Al
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023, 4:11 PM Stan Dye <standye@...> wrote: It is not uncommon for the sma-terminated pigtail cables that come with the
nanovna to fail, or to not have been assembled well. Sometimes the shield
is not soldered at the connector, so it passes test at the factory, but
fails the first time you bend it. I ordered a set of better sma pigtail
cables, and haven't had a problem with them.
On Wed, Sep 6, 2023, 2:51 PM Allan Johnston <adhjohnston@...> wrote:
Dave, W0LEV,
It's looking like an intermittent good then bad connection with the
NanoVNA.
The nanovna is connected with the unit's supplied connectors/coax and
additional connector as needed for the antenna.
See attached "nanovna usual bad trace" jpeg that shows the connectors.
The RigExpert connection does not include the small diameter nanovna coax
cable.
As I set up the RigExpert and NanoVNA for review and photos I discovered
the flaky intermittent connection in the run of small coax and connectors.
The bad connection is so random that I cannot tell what connector is the
problem.
More hunting!
Thank you for your response. Your questions helped me discover what is
biting me. At least I know the NanoVNA is working.
If you or anyone else has comments on the trace or the
equipment/coax/connector setup that may help me out then please don't
hesitate to respond.
Al. KA0VIA
On Wed, Sep 6, 2023 at 12:31?PM W0LEV <davearea51a@...> wrote:
How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the
NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you
verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...>
wrote:
The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The
RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter
antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Glad you found the problem. These cables have been problematic from day
one. I've even had a few with the NANOVNAs. Even a few bad USB cables.
Dsve - W?LEV
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023 at 8:51?PM Allan Johnston <adhjohnston@...> wrote: Dave, W0LEV,
It's looking like an intermittent good then bad connection with the
NanoVNA.
The nanovna is connected with the unit's supplied connectors/coax and
additional connector as needed for the antenna.
See attached "nanovna usual bad trace" jpeg that shows the connectors.
The RigExpert connection does not include the small diameter nanovna coax
cable.
As I set up the RigExpert and NanoVNA for review and photos I discovered
the flaky intermittent connection in the run of small coax and connectors.
The bad connection is so random that I cannot tell what connector is the
problem.
More hunting!
Thank you for your response. Your questions helped me discover what is
biting me. At least I know the NanoVNA is working.
If you or anyone else has comments on the trace or the
equipment/coax/connector setup that may help me out then please don't
hesitate to respond.
Al. KA0VIA
On Wed, Sep 6, 2023 at 12:31?PM W0LEV <davearea51a@...> wrote:
How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...>
wrote:
The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter
antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
--
*Dave - W?LEV*
--
Dave - W?LEV
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
It is not uncommon for the sma-terminated pigtail cables that come with the
nanovna to fail, or to not have been assembled well. Sometimes the shield
is not soldered at the connector, so it passes test at the factory, but
fails the first time you bend it. I ordered a set of better sma pigtail
cables, and haven't had a problem with them.
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023, 2:51 PM Allan Johnston <adhjohnston@...> wrote: Dave, W0LEV,
It's looking like an intermittent good then bad connection with the
NanoVNA.
The nanovna is connected with the unit's supplied connectors/coax and
additional connector as needed for the antenna.
See attached "nanovna usual bad trace" jpeg that shows the connectors.
The RigExpert connection does not include the small diameter nanovna coax
cable.
As I set up the RigExpert and NanoVNA for review and photos I discovered
the flaky intermittent connection in the run of small coax and connectors.
The bad connection is so random that I cannot tell what connector is the
problem.
More hunting!
Thank you for your response. Your questions helped me discover what is
biting me. At least I know the NanoVNA is working.
If you or anyone else has comments on the trace or the
equipment/coax/connector setup that may help me out then please don't
hesitate to respond.
Al. KA0VIA
On Wed, Sep 6, 2023 at 12:31?PM W0LEV <davearea51a@...> wrote:
How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...>
wrote:
The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter
antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
Dave, W0LEV,
It's looking like an intermittent good then bad connection with the NanoVNA.
The nanovna is connected with the unit's supplied connectors/coax and
additional connector as needed for the antenna.
See attached "nanovna usual bad trace" jpeg that shows the connectors.
The RigExpert connection does not include the small diameter nanovna coax
cable.
As I set up the RigExpert and NanoVNA for review and photos I discovered
the flaky intermittent connection in the run of small coax and connectors.
The bad connection is so random that I cannot tell what connector is the
problem.
More hunting!
Thank you for your response. Your questions helped me discover what is
biting me. At least I know the NanoVNA is working.
If you or anyone else has comments on the trace or the
equipment/coax/connector setup that may help me out then please don't
hesitate to respond.
Al. KA0VIA
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023 at 12:31?PM W0LEV <davearea51a@...> wrote: How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...>
wrote:
The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: Nano VNA of a modified 40m hor loop NVIS antenna
Thank you for the reply. I¡¯m a long time NVIS emcomm loop user but I just moved and purchased the H4 to build a new loop for 80 and another for 40. I¡¯ve had excellent success using the 10KW common mode 1:1 coax to ladder line balun from DXE with a short run of LMR400 to the outside and then the ladder up to the loop. JJ Knight N5MNX ________________________________ From: [email protected] < [email protected]> on behalf of W0LEV <davearea51a@...> Sent: Wednesday, September 6, 2023 12:12:55 PM To: [email protected] < [email protected]> Subject: Re: [nanovna-users] Nano VNA of a modified 40m hor loop NVIS antenna 40-meters between your target times of 1000 to 1400 local will be problematic if the fof2 is not at or above 7-MHz. Here in N. Colorado, of late, it has been, but over the last couple of years during the lull between Solar Cycles 24 and 25, NVIS was impossible due to the low fof2 which came in lower than 5 MHz. For a look at the fof2 in your area, check the following: <> Of course, I regularly use the Boulder, Colorado, ionogram as it's only some 30-miles to my south. Dave - W?LEV On Wed, Sep 6, 2023 at 11:58?AM Barry K3EUI <k3euibarry@...> wrote: JJ Night
To answer your question¡
There is nothing special about this antenna, other than it is a closed
LOOP of 140 ft heavy wire #10 because I had a few hundred feet of this wire.
I wanted good daytime NVIS antenna for prop of only a few hundred miles
from Phila around 10AM to 2 PM.
I was not interested in a low-angle DX signal for evening use (I have a
vertical that does that well)
The amount of wire did not matter too much (120-140 ft to start).
I feed this with about 75 ft of RG213 (nothing special)
The shape is a rectangle, only 20 ft or so above ground. I had a few big
strong trees as tie points.
I tried a 4:1 balun at first (thinking impedance of 100 ohms) and that did
not work well.
I replaced that with a simple 1:1 BALUN (choke).
At the low height above ground, I expected a lower impedance than putting
it up 50 ft.
I could attach the Nano VNA right at the feedpoint - direct - to avoid the
feedline messing with impedance.
I then hooked it up to a CLC Tuner (in my shack) in case the SWR was high
at the digi part of the band.
Because I had about 140 ft wire in the loop, the resonant point was just
below 7 MHz (about 6.8 MHz).
It worked fine for two weeks, but then I thought maybe I could improve it
by shortening it.
I pruned it back about 10 feet (harder to do for me on a 90 degree day)
and then I saw that the minimum SWR fell around 7.1 MHz, right where I
wanted it.
The NANO VNA that I own is already 3 years old (Amazon model) and I¡¯m
using NANO VNA SAVER app on a Win10 (10 yr old) desktop. I had to make the
CALIB first with a 3-30 MHz span at a 10x mag. That took a few minutes to
do the OPEN, SHORT, and 50 0hm LOAD with the standards that came with the
rig.
I did a sweep from 3-30 MHz using the 50 ohm standard and everything
looked perfect on the 6 graphs.
That was reassuring!
The closed loop works far better than a pair of Hamsticks mounted
horizontally (14 ft total). Well, obviously!
It works just about as well as a simple 66 ft Inverted V center-fed dipole
(my standard) but I see much less QSB on the closed loop than from the
dipole. I like to use 7047 kHz W1AW CW bulletins as my standard to compare
antennas at 9AM to 10AM. And¡ it helps me copy CW by ear.
So nothing special about anything that I did.
I put in a CLC tuner in my shack, and this does sharpen up all of the
graphs, but I did not really need it.
My goal: see if I could build a better DAYTIME NVIS antenna for low part
of the 40m band.
I love the sound card digi modes and FLDIGI and am working on a new 40m
EMCOMM digi mode net which should begin on October 1st: Mid-Atlantic 40m
NBEMS net (7068 kHz vfo).
We plan to run this net every Sunday at 10AM to 11AM for a few months to
see how well ¡°fickle forty¡± does at that hour with THOR22 (checkin) and
THOR56 (traffic). We know that 80m collapses by 10 AM for NVIS.
I really did not need a Nano VNA to build and test this antenna. I am now
doing A/B tests to see if folks I work on 40m digi modes can hear any
differences between the closed loop and Inverted V simple dipole.
I took the back-to-back Hamsticks down (may be good for a portable setup)
And I still have a 36 ft vertical with two above ground radials (upside
down T) for evening DX.
What are you trying to accomplish in your antenna?
Without the SAVER software, I¡¯d be lost (color blind).
de k3eui Barry
near Philly
Sept 06 2023
-- *Dave - W?LEV* -- Dave - W?LEV
|
Re: updated and calibrated nanovna h4 yields incorrect swr readings
How are you connecting the NANOVNA? Identical to the method used for the
RigExpert? Where does the trace show on the Smith Chart of the NANOVNA?
Is the trace consistent with the SWR indication?
Once your NANOVNA is calibrated, have you gone back with your cal.
standards and verified the calibration took correctly? Have you verified
your cal. standards on the RigExpert or some other method?
I know.....just a bunch of questions, but I'm searching for possible
problems.
Dave - W?LEV
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023 at 5:27?PM Allan Johnston <adhjohnston@...> wrote: The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert
AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The RigExpert
AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter antenna
that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
-- *Dave - W?LEV*
--
Dave - W?LEV
|
updated and calibrated nanovna h4 yields incorrect swr readings
The Nanovna h4 in use was purchased from R&L Electronics a year or so ago.
Last month I updated the software.
The Nanovna has never given me "good" results as compared to a RigExpert AA 650 zoom when measuring HF, VHF or UHF antennas.
The Nanovna has been calibrated for each frequency range. The RigExpert AA-650 zoom passes the self test.
Example; the Rigexpert reads a SWR of close to 1:1 for a 2 meter antenna that is externally mounted while the Nanovna results show 50:1.
Any ideas?
Thanks,
Al, KA0VIA
|
Re: Nano VNA of a modified 40m hor loop NVIS antenna
40-meters between your target times of 1000 to 1400 local will be
problematic if the fof2 is not at or above 7-MHz. Here in N. Colorado, of
late, it has been, but over the last couple of years during the lull
between Solar Cycles 24 and 25, NVIS was impossible due to the low fof2
which came in lower than 5 MHz. For a look at the fof2 in your area, check
the following:
Of course, I regularly use the Boulder, Colorado, ionogram as it's only
some 30-miles to my south.
Dave - W?LEV
toggle quoted message
Show quoted text
On Wed, Sep 6, 2023 at 11:58?AM Barry K3EUI <k3euibarry@...> wrote: JJ Night
To answer your question¡
There is nothing special about this antenna, other than it is a closed
LOOP of 140 ft heavy wire #10 because I had a few hundred feet of this wire.
I wanted good daytime NVIS antenna for prop of only a few hundred miles
from Phila around 10AM to 2 PM.
I was not interested in a low-angle DX signal for evening use (I have a
vertical that does that well)
The amount of wire did not matter too much (120-140 ft to start).
I feed this with about 75 ft of RG213 (nothing special)
The shape is a rectangle, only 20 ft or so above ground. I had a few big
strong trees as tie points.
I tried a 4:1 balun at first (thinking impedance of 100 ohms) and that did
not work well.
I replaced that with a simple 1:1 BALUN (choke).
At the low height above ground, I expected a lower impedance than putting
it up 50 ft.
I could attach the Nano VNA right at the feedpoint - direct - to avoid the
feedline messing with impedance.
I then hooked it up to a CLC Tuner (in my shack) in case the SWR was high
at the digi part of the band.
Because I had about 140 ft wire in the loop, the resonant point was just
below 7 MHz (about 6.8 MHz).
It worked fine for two weeks, but then I thought maybe I could improve it
by shortening it.
I pruned it back about 10 feet (harder to do for me on a 90 degree day)
and then I saw that the minimum SWR fell around 7.1 MHz, right where I
wanted it.
The NANO VNA that I own is already 3 years old (Amazon model) and I¡¯m
using NANO VNA SAVER app on a Win10 (10 yr old) desktop. I had to make the
CALIB first with a 3-30 MHz span at a 10x mag. That took a few minutes to
do the OPEN, SHORT, and 50 0hm LOAD with the standards that came with the
rig.
I did a sweep from 3-30 MHz using the 50 ohm standard and everything
looked perfect on the 6 graphs.
That was reassuring!
The closed loop works far better than a pair of Hamsticks mounted
horizontally (14 ft total). Well, obviously!
It works just about as well as a simple 66 ft Inverted V center-fed dipole
(my standard) but I see much less QSB on the closed loop than from the
dipole. I like to use 7047 kHz W1AW CW bulletins as my standard to compare
antennas at 9AM to 10AM. And¡ it helps me copy CW by ear.
So nothing special about anything that I did.
I put in a CLC tuner in my shack, and this does sharpen up all of the
graphs, but I did not really need it.
My goal: see if I could build a better DAYTIME NVIS antenna for low part
of the 40m band.
I love the sound card digi modes and FLDIGI and am working on a new 40m
EMCOMM digi mode net which should begin on October 1st: Mid-Atlantic 40m
NBEMS net (7068 kHz vfo).
We plan to run this net every Sunday at 10AM to 11AM for a few months to
see how well ¡°fickle forty¡± does at that hour with THOR22 (checkin) and
THOR56 (traffic). We know that 80m collapses by 10 AM for NVIS.
I really did not need a Nano VNA to build and test this antenna. I am now
doing A/B tests to see if folks I work on 40m digi modes can hear any
differences between the closed loop and Inverted V simple dipole.
I took the back-to-back Hamsticks down (may be good for a portable setup)
And I still have a 36 ft vertical with two above ground radials (upside
down T) for evening DX.
What are you trying to accomplish in your antenna?
Without the SAVER software, I¡¯d be lost (color blind).
de k3eui Barry
near Philly
Sept 06 2023
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Re: Nano VNA of a modified 40m hor loop NVIS antenna
Capacitor,inductor,capacitor Ok... with a capacitor, inductor, capacitor + inducteur you can do a fixed two band matching network :) Thank -- F1AMM Fran?ois -----Message d'origine----- De la part de Jim Lux Envoy¨¦ : mercredi 6 septembre 2023 15:49
|
Michael A. Terrell
