On Oct 26, 2006, at 2:26 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 24, 2006, at 5:18 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

On Oct 24, 2006, at 1:35 AM, pentalab wrote:

### This sucks... and I don't like it one bit.

RICH SEZ... So use Matsushita/Panasonic MOFs instead of wire-

wounds.

######## I"M MOT USING WIRE WOUNDS !!!

### Or should I not think about it... and hope my 24 x new

2500 > UF @ 450 V lytics don't got off like firecracker's
someday ??

RICH SEZ... To me, it sounded more like a jumbo cherry bomb.

Panasonic MOF resistors are pretty reliable.

### Not reliable enough for me. Just one MOF reistor out of a
string of 24-30 has to open up... and it's gonna leave one
expensive mess to clean up.

We have probably sold 13 or 14 1k-unit boxes of Matsushita 100kΩ, 3w
MOF resistors and none have reportedly failed. Me thinks you
worryeth too much, brother James.

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., FRANCIS CARCIA <carcia@...>
wrote:

Lower frequency you need more primary turns so a higher tap to

reduce heating but this will reduce the output voltage due to turns
ratio change, gfz

### agreed. So, in essence... to properly run a xfmr on 50
hz.... you require MORE turns on the pri... and to keep the
turns ratio the SAME.... you will also have to add MORE turns on
the sec..... which the TL-922 may well allready have. The
UK/JA/ZL/VK have 50 hz power, so unless the NA version is 60 hz
only.... I'm guessing any oversea's 922 xfmr's will run just
fine on either freq.

### Too bad somebody way back when, didn't decide on something
higher.... like 70-80-90-100 hz power..... or even higher.. like
200 hz. These plate xfmr's, blower's, and eveything else could
have been made smaller.. and more eff.

### This is the problem with setting standards with 'new'
technology... they get outdated... fast.

Later.....Jim VE7RF

Lower frequency you need more primary turns so a higher tap to reduce heating but this will reduce the output voltage due to turns ratio change,?gfz

pentalab wrote:

开云体育

--- In ham_amplifiers@..., "Hsu" <Jbenson@...> wrote:

Thanks,Will
Could tell me the power rating of TL922 HV transformer?
Thanks again!
73! Hsu
----- Original Message -----

#### HSU.... as far as I know.... from memeory... the plate
xfmr in a TL-922 is rated at aprx 1.2 KVA CCS. The RL Drake
plate xfmr, used in the L4/L4-B/ L-7 is also rated at 1.2 KVA
CCS.

#### In the case of the RL drake xfmr.... that rating is for 60
hz only..... and like Will sez.... it MUST be de-rated for 50
hz. Several VK/ZL's I have spoken too over the years have
complained of over heating the RL drake xfmr, when run on 50 hz.

### Dunno about the TL-922 xfmr. On my old yaesu FL-2100 B
[1977] , it had primary taps for 100/120 200/240.... in Japan
they use 100/200 V and 50 hz. So In that case, I'd assume
the yaesu plate xfmr would run on 50 hz.

### IF the TL-922 xfmr has pri taps for 100/200v.... you can
asume it will run ok on 50 hz. IF it only has taps for
120/240... then asume it's 60 hz only. It seems to me that
the TL-922 is popular in the UK... and I believe they use 220 v 50
hz.

### In normal operation... the TL-922 xfmr would be good for
600 w output RTTY/ FM CCS..... and 1200 w out pep on ssb.... and
maybe a little less on CW.

### I agree with Will. You can't go by weight alone. Case in
point, the Hammond 795 series plate xfmr's weigh in at 80 lbs
[36 kg] , are rated for 2.2 kva CCS.... and run VERY hot when
used in a C input filter.... and when running 1900w PEP output
from the linear.

### In the case of the Hammond, it was a high reactance type,
with a center tap, designed for tube rectifier's... and had a high
68 ohm sec DC resistance. The drake L4B plate xfmr has a 10
ohm DC sec... is made for a C input filter.. and is of the LOW
reatance type.... the TL-922 and the SB-220 both have 10 ohm dc
resistance secondaries.

### These Peter Dahl hypersil C core plate xfmr's flat out won't
blow up, or overheat, doesn't matter what you do to em. They are
either the most underated things, or the greatest things since
sliced bread... take ur pick.

Later... Jim VE7RF

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 24, 2006, at 5:18 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

On Oct 24, 2006, at 1:35 AM, pentalab wrote:

### This sucks... and I don't like it one bit.

RICH SEZ... So use Matsushita/Panasonic MOFs instead of wire-

wounds.

######## I"M MOT USING WIRE WOUNDS !!!

### Or should I not think about it... and hope my 24 x new

2500 > UF @ 450 V lytics don't got off like firecracker's
someday ??

RICH SEZ... To me, it sounded more like a jumbo cherry bomb.

Panasonic MOF resistors are pretty reliable.

### Not reliable enough for me. Just one MOF reistor out of a
string of 24-30 has to open up... and it's gonna leave one
expensive mess to clean up.

### Flash ! with 4 x resistor's per cap... and one cut

loose. [assuming caps are no more than 75% of their v rating]

The

one cap with the bad R will be almost maxed out.

RICH SEZ... That would work.

### 4 x resistor's in parallel = 25 K = lotsa heat per
cap. Probbaly 6-8 x resistor's.... each say 600-800K...

all

in parallel... PER cap, would be the ultimate solution.....

then if anything opened up.... no chance of all ur caps

blowing up. The heat would be zip... per resistor.

########### Here's my problem Rich.... Those 2500 Uf @ 450 V

CD brand 10 A CCS ripple current rated caps I got NEW, by the case

load are listed at an unreal price tag.... like $100.00

EACH... in single lot quantities. I have 72 of em... and will be
using em in groups of 24. I got em dirt cheap... they all
tested good, when checked on the bench. I would be just pissed
if they started exploding cuz of even the remotest chance of one
resistor lead opening.

RICH SEZ So don't use WW resistors to equalize them.

### You still don't get it ! I'm NOT using wirewounds !! I
don't trust these MOF's either. My other concern with 24-30 x
100 K MOF's is.... they don't draw enough bleeder current to swamp
out the typ leakage current of a string of caps.

### So... the real solution [aside from the usual 1 kv-6A

safety

diode, rvs connected across eacg lytic] is to parallel 6 x 300 K
MOF resistors across EACH cap. [50 K for the paralled mess].

What is the V-rating and P rating of the 300k resistors?

##### Should be the same as 100 K MOF's... about 500 V.

If one ever opened... the voltage would only increase 20%

on

that one cap. Total diss is 53 W. Each of the 144

resistor's

would only dissipate .37 w. Heck, with 6 x 150 K
resistors, Total diss rises to 106 W.... or a measely .74

watt

for each of the 144 resistor's.

### For a 8000 V [no load] supply... with 24 x caps.....

normal V

per cap is 333 V [74% of the 450 V max rating]. With 6 x

300K /6

x 150 K resistor's across each cap.... and say one of the 6

opened

up.... V across that one cap will increase to 400 V.......well
within the 450 V rating of the cap....... end of problem.... end

of story.

### later...... Jim VE7RF






Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

I think they more or less took the suggestion from a plastics

peddler saying that Delrin would for sure work in this application.
I'll have to look up the difference in the D factor between Delrin
and say Teflon, etc. I have the Modern Plastics Encyclopedia here,
I've just not looked through it in a while.

### I looked this up months ago. Seems to me, the difference
between the D factor between Delrin [Delin is sold under the trade
name of "Polypenco"] and Teflon was astronomical. Teflon comes
in solid rods, comes in any diam u want. After hearing about one
too many horror stories about Delrin... I said.. lets go with
Teflon... esp for making the home made plate chokes. [big one is
180 uh... small one is 45 uh, both are wound on 1" diam solid
teflon] We also used 1" diam solid teflon to make the 45
uh ..."safety choke". Every plastic shop 'expert' I deal with
hasn't a clue about their products and RF. The best they can
usually do is just hand you the "data sheet".

### another alternative is hollow teflon tubing... usually 1/8"
thick... or thicker. My buddy found a source for this hollow
teflon tubing in Quebec some where... and if I find out where...
I'll let every one know. It was a LOT cheaper than the solid
stuff. The end user would insert a tight fitting plug in the
bottom... so the plug could be tapped and drilled with the usual
1/4-20/27 threads. The solid teflon stuff is not that expensive...
fairly cheap and sold by the foot... not much more than Delrin...
which I would NOT trust for some applications.

### some of my buddies have had great success with Delrin in
plate chokes,, and standoffs, safety chokes etc... some have said
the tops of the chokes would burn off.

### Beware... a LOT of these old and new amp projects[plus
commercially made stuff] will use plane jane 2.5 mh rf choke
as the "safety choke" wired between 50 ohm output and chassis on
a PI-L.... and between load cap and chassis on a simple PI-net. I
measured a bunch of em... and some are as high as 40 ohms dc
resistance. In one case, a contester buddy of mine, had the
plate block cap short out.... and the safety choke blew into a
million pieces! I wouldn't trust ANY of these mickey mouse pi-
wound chokes as "safety chokes". Don't believe me..... wire
one between the B+ and B-.... [via a heavy duty vac relay]...
out in ur back yard.... hit the switch.. and watch the back yard
blow up !

### Then I noticed all the big boys use a simple 40-50 uh
solenoid choke... wound with 16-18ga magnet wire. Henry radio
does this on the 8-K... and creative electronics [now amp systems
inc] also does the same... ditto with harris, etc. What else
that will work as a.. "safety choke" is 10-18 ga magnet wire,
wound on a 1.6" torroid. In all cases, you are looking for 35-50
uh... and NO series resonances in bands of interest. The 45 uh
chokes we use on 1" diam solid teflon, are wound with 18 ga magnet
wire... and easily handle the 8 KV on the 135 uf cap filter + 50
ohm, 450 W glitch R + HV fuse. In once case, the strap from
the C1 vac tune cap was not even finger tight, flopped over.. and
was only 1/8" away from the parasitic suppressor assy...
arced... and 8 KV went through the entire PI NET.... nothing
happened.. as the 45 uh safety choke simply shorted the B+ to
the chassis.... from there it went through the PARALLELED 1 kv-
6A diodes [800A surge rated for the pair]... which are installed
between chassis and B- completing the loop... and bam... HV
fuse pops in <2 msecs.

### we have tested this 45 uh safety choke a 1/2 doz times
now.... it has no visible signs of deformation.

What material is used now?

### I think Will thought they were using Micarta... but all
Micarta I have seen. [I use a lot of it] is usually bright red.
I have never seen Micarta in anything but red.

### I also noticed in cat #8, SSON had these deluxe new, custom
made for em... 500 pf- 9 kv air variables.... supposedly for
tuners... well made... and about $115 If I remember correctly.

Later.........Jim VE7RF

Hi Noel

I built a 2m amplifier a couple of years ago using a pair of GI-7b triodes. It has been absolutely trouble free except for one flash over when I accidently grossly over-drove it. That took out the HT glitch resistor as well as the transformer primary fuse but both tubes survived and are still in operation. The amp has been used (and won) several 2m contests here in the UK and I regularly run it using WSJT which is a high duty cycle mode.

25 watts of drive gives me the UK legal limit of 400 watts out. The maximum I get out of this pair on 2m with about 1700V on them is 700 watts.

This amplifier is online at BTW I wouldn't have dared post that link in the old Amps group! I'd have been torn to shreds!! But I know in here any criticism will be helpful and positive.

The tubes only cost me UK 15.00 each including postage from Russia. It's difficult to beat that for low cost.

I'm thinking along similar lines to you now and may also build a HF RF deck. I wouldn't hesitate to use the same tubes again. Their slightly bigger brother the GI-46 is supposed to give more power out. It's a bit more expensive but would also be worth considering.

73 Paul G4DCV

vk4hr wrote:

All,

I'm writing a program to calculate the numbers on power transformers.
I named it Maxwell, as I figured he was the first to come up with the
formulas himself. I uploaded the pics to the photo directory for this
group. I will eventually have this for sale as shareware in the near
future. Are there any thing you would like to see added to it? All
comments are welcome.

Thanks,

Will

Noel,

Please see this page for lots of links to both retrofits and homebrew amps using the GI-7B including one in progress by Bob,VK3ZL: <>

73, Tony W4ZT

vk4hr wrote:

First post from a new member and already asking questions.
Has anyone had any experiences "good or bad" with the Russian GI7B
tubes. Just chasing information for a club project a "single band amp"
for possibly 40 or 20.

Noel
VK4HR

Hsu,

That formula is for 60 Hz, I forgot to add that. The
difference between 50 Hz and 60 Hz transformer size is
a factor of 1.2. A 50 Hz transformers core will be 1.2
times larger than a 60 Hz for an equivelant power output.

Best,

Will


--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

Hsu,

There's a short formula one can use to estimate the power by the

core

area providing they have the wire sized right. You use the core

area

(a) in square inches. A hint to make it easy to measure is the
outside leg of a transformer is most always 1/2 as wide as the core
width. So multiply the leg width by 2 to find the core width. Next,
multiply that by the irons stack thickness and that will give the
area. The formula works with 12 kilogauss. If they're running it
higher, the core could be smaller for the same power rating. You'll
have to convert centimeters into inches as the formula is for

square

inches. Theres 2.54 centimeters in a lineal inch. To convert into
square centimeters, multiply square inches by 6.45.

a = (leg width in inches x 2) x cores stack thickness in inches

P = ( a / 0.1725 )^2

This will get you close.

Best,

Will



--- In ham_amplifiers@..., "Hsu" <Jbenson@> wrote:

Thanks,Will
Could tell me the power rating of TL922 HV transformer?
Thanks again!
73! Hsu
----- Original Message -----

Hsu,

There's a short formula one can use to estimate the power by the core
area providing they have the wire sized right. You use the core area
(a) in square inches. A hint to make it easy to measure is the
outside leg of a transformer is most always 1/2 as wide as the core
width. So multiply the leg width by 2 to find the core width. Next,
multiply that by the irons stack thickness and that will give the
area. The formula works with 12 kilogauss. If they're running it
higher, the core could be smaller for the same power rating. You'll
have to convert centimeters into inches as the formula is for square
inches. Theres 2.54 centimeters in a lineal inch. To convert into
square centimeters, multiply square inches by 6.45.

a = (leg width in inches x 2) x cores stack thickness in inches

P = ( a / 0.1725 )^2

This will get you close.

Best,

Will

Thanks,Will
Could tell me the power rating of TL922 HV transformer?
Thanks again!
73! Hsu

Jim,

Did you ever try paper tubing for the chimneys? It's the same
kraft paper they use in transformer insulation. No hotter than
a tube gets with the blower running, it wont hurt anything.
This stuff is made in 10 foot lengths but can be bought
shorter through paper suppliers that make and sell cardboard
boxes, etc. A company named U-Line has a good selection of
large diameter tubing that would make a good chimney. A compamy
who makes the tubing is Precision Paper Tube. They make the
tubing used in inductors, etc.

Another way is to fabricate one from fish paper, or the
blue-grey stuff used again as transformer insulation. It has
a clay added to it. It runs well as a chimney and one can roll
it up as a cone shape so its wider at the bottom as in some
chimneys.

The last is to make a fiberglass chimney. One can buy the
fiberglass sheet and the resin from Sears and some
auto-body suppliers. Sears carries it in their boat
specialties catalog. You'd have to make a form for say a
cone shape out of teflon so the resin wont stick to it.
An aluminum form might work to using a release agent.

Best,

Will



--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

Gents

I just posted some new pix.[page-3 of my pix page]..... depicts

how

we paralleled the 3 x wafers of the Model 85 switch. We
used 1" wide CU strap... x .022" thick... formed into a..."U".
Each strap was formed on some scrap square material..... forget
the precise width... believe it was aprx 3/8" wide. This
allows for maintaining the 13 KV air gap between adjacent
contacts. Using 1" wide strap... in a "U", also allows for
zip stray L through the 3 x wafer's... and also will handle
literally globs of RF current.


Wafer at back end... closest to tank coil, we call wafer #1....
this is where the various coil taps terminate. The wafer
closest to the front panel/knob, is wafer #3. The output of
this switch is on wafer #3..... which of course, feeds both the vac
load cap and the low freq end of the huge Multronics Jumbo tank
coil. This "in on wafer #1.. and out on wafer #3" allows for an
almost even RF current sharing, between the 3 x paralleled

wafers.

This same scheme has also been done on a model #88 switch. Just
make sure you use "double commons" on all 3 x wafers.. on any of
these series of switch's. The double commons allows grabbing
the central rotor hub on BOTH sides.... handles WAY more RF

that

way. Stock, they only come with one common per rotor... grabbing
the rotor on the top side only. Skip Coleman at Multi-tech
Industries supplied me with all the bits and pieces I needed
for my model 85 and 88 switch's. There is also a pix depicting
the "double commons" portion of the switch... [page 2 of pix

page]

The next pix just shows a close up of the surplus [$20.00]
Multronics 14 uh tank coil model MI-14 [it actually measures
12.2 uh] It came with just one multronics 1/2" tubing
clamp. A friendly machinist made a bunch more for us... virtual
carbon copies too ! Good thing too... since Multronics wanted
$50.00 for EACH tubing clamp ! ....ouch. Taps from the triple
wafer bandswitch to the Multronics coils, etc... was done using
1" wide flat strap x .022" thick.... zip stray inductance....
even though most of the taps were very long. Else where on the

pix

page... shows the HB 1/2" tubing coil.. smaller ID [3"] used
for 20-17-15m.... it was added to the HF end of the 12.2 uh
Multronics coil....which has a huge ID to it. Tapped for 160-

80-

60-40-30-20-17-15m.... NO 10/12m.

The last new pix, shows the 1 in 9 out 15 kw remote ant
switch... from a different angle. The strap is all 3/4" wide
x .022" thick... spaced aprx 5/16"... which gives us 50 ohms.
Although the DPDT relays are rated for just 277 Vac... they
hi - pot tested to 3 kv..... and have had as much as 17 kw

pumped

through em........ surplus $4.00 each. 12 vdc. I

previously

posted the url for both these surplus 12 vdc DPDT relays... and
also the 3 x pole contactor's [with 220 v coil].

Later........ Jim VE7RF

Gents

I just posted some new pix.[page-3 of my pix page]..... depicts how
we paralleled the 3 x wafers of the Model 85 switch. We
used 1" wide CU strap... x .022" thick... formed into a..."U".
Each strap was formed on some scrap square material..... forget
the precise width... believe it was aprx 3/8" wide. This
allows for maintaining the 13 KV air gap between adjacent
contacts. Using 1" wide strap... in a "U", also allows for
zip stray L through the 3 x wafer's... and also will handle
literally globs of RF current.


Wafer at back end... closest to tank coil, we call wafer #1....
this is where the various coil taps terminate. The wafer
closest to the front panel/knob, is wafer #3. The output of
this switch is on wafer #3..... which of course, feeds both the vac
load cap and the low freq end of the huge Multronics Jumbo tank
coil. This "in on wafer #1.. and out on wafer #3" allows for an
almost even RF current sharing, between the 3 x paralleled wafers.

This same scheme has also been done on a model #88 switch. Just
make sure you use "double commons" on all 3 x wafers.. on any of
these series of switch's. The double commons allows grabbing
the central rotor hub on BOTH sides.... handles WAY more RF that
way. Stock, they only come with one common per rotor... grabbing
the rotor on the top side only. Skip Coleman at Multi-tech
Industries supplied me with all the bits and pieces I needed
for my model 85 and 88 switch's. There is also a pix depicting
the "double commons" portion of the switch... [page 2 of pix page]


The next pix just shows a close up of the surplus [$20.00]
Multronics 14 uh tank coil model MI-14 [it actually measures
12.2 uh] It came with just one multronics 1/2" tubing
clamp. A friendly machinist made a bunch more for us... virtual
carbon copies too ! Good thing too... since Multronics wanted
$50.00 for EACH tubing clamp ! ....ouch. Taps from the triple
wafer bandswitch to the Multronics coils, etc... was done using
1" wide flat strap x .022" thick.... zip stray inductance....
even though most of the taps were very long. Else where on the pix
page... shows the HB 1/2" tubing coil.. smaller ID [3"] used
for 20-17-15m.... it was added to the HF end of the 12.2 uh
Multronics coil....which has a huge ID to it. Tapped for 160-80-
60-40-30-20-17-15m.... NO 10/12m.

The last new pix, shows the 1 in 9 out 15 kw remote ant
switch... from a different angle. The strap is all 3/4" wide
x .022" thick... spaced aprx 5/16"... which gives us 50 ohms.
Although the DPDT relays are rated for just 277 Vac... they
hi - pot tested to 3 kv..... and have had as much as 17 kw pumped
through em........ surplus $4.00 each. 12 vdc. I previously
posted the url for both these surplus 12 vdc DPDT relays... and
also the 3 x pole contactor's [with 220 v coil].

Later........ Jim VE7RF

On Oct 25, 2006, at 1:04 PM, craxd wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 24, 2006, at 9:05 PM, craxd wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

...
Correct. He didn't like the fact that an oscilloscope indicated a
worst-case potential in a SB-220 that was only about 1/3 of what he
predicted it would be. This potential is on the verge of arcing the
Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said was
parasitic arcing by the SB-220's occasional 110MHz oscillation.

The peak or peak to peak voltage one reads is exact,...

Porcine shampoo. I'm a guy who used to calibrate oscilloscopes.

Wouldn't you agree they're exact to within their tolerance?

No. Exact means without error -- within tolerance means within a specified error.

If the cal equipment used is correct, and the scope is ran
in a similar enviroment temperature wise, etc, it should show
close to the same as what it was calibrated to read.

Correct -- which is not without error.

That is
provided it's withing calibration and hasn't been tampered
with. I'm not saying it's exact with no deviation, but it's
one of the most exact ways we have reading an AC voltage. 3%
or less tolerance is pretty darn good. According to the
Tektronix manuals, they should be capable of better than 3%.

A calibrated oscilloscope is one way power meters can be

calibrated

and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.

Well it's according to what you term clean. Harmonics no, unless

you

build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope.

But not SSB IMD.

...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Best,

Will





Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

MFJ does sell a stand alone dip meter that's decent as I have
one of them. MFJ doesn't manufacture this meter either, they
have them branded by an asian manufacturer. It's the same dip
meter as the Leader solid state and a few others. I'd trust
it more than the analyzers that MFJ made by a long shot.

I compared the one they're selling to the Heathkit one I have,
and they work similar to the same.

Best,

Will


--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 24, 2006, at 2:49 PM, pentalab wrote:

--- In ham_amplifiers@..., Bill Turner <dezrat@>
wrote:

ORIGINAL MESSAGE:

On Mon, 23 Oct 2006 00:20:30 -0000, "craxd" <craxd1@>
wrote:

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision.

------------ REPLY FOLLOWS ------------

One needs to be careful with this. The typical single-tube or
single-transistor dip meter can be pulled considerably off the

true

resonant frequency if coupling is very tight to a high-Q circuit.

Just

physically move the dip meter away far enough so the dip is

barely

perceptible and the accuracy will improve greatly.

If you have used a dip meter much, you have no doubt had the
experience of tuning slowly across the dip, and as you continue

tuning

have the dip suddenly disappear as the pulling effect disappears.
Loose coupling will prevent this from happening.

### Highly agreed. Loose coupling is as good as it gets.... for
acuracy anyway. Mike Stahl, K6MYC warned me about this 25 yrs
ago.... he didn't trust em.. when tweaking yagi's.... I wouldn't
either.

According to a friend who loaned him a dipmeter, he did not

realize

that a plug-in coil had to be inserted to make it work.

### For a real laff.... I bought the "mating" grid dip osc
coils for my MFJ-259 analyzer. Two coils cover the entire
spectrum. I can't grid dip ANYTHING with em... even simple
stuff.. like a coil in parallel with a cap... on the test bench.
Then I find out nobody else can grid dip anything either! Then

Rauch

sez they don't really work. They still don't. It was
suggested not to buy the optional coil(s).

With MFJ, $elling is the object, working is not

...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org