Adjusting Ameritron AL-82 input coils
I have an older AL-82 that works fine except the input SWR is right around 2:1 on 20m and it's just high enough to cause the K3 that I am driving it with to start to foldback so that the output power is 1200w max. Not that another couple hundred watts will
really make a difference, but I thought I would try and adjust the input match coil slug on 20m.
This older unit has what kind of looks like a cap on the coils. It has a flat blade screwdriver slot and also a larger hole in the center that looks like a hex tool would fit into. However, when trying even a larger hex tool through it, no less the plastic
tuning tool I bought from DX Eng, of course with the unit off and discharged, it appears there isn't a tuning slug inside? Is the outside cap meant to rotate?
I also have a much newer AL-82, and it doesn't have these "covers" on the coils and I can clearly see a tuning slug inside each coil.
It looks like a job to get to this box to see the inside. Has anyone experienced adjusting the tuned inputs on an older AL-82?
TU;
Steve
NY3A
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Re: Bird Termaline load repair
Maybe you can make a short jumper with some L or C (which ever's needed) to tune out the reactance at those UHF freqs? Bob W4JFA?
In? lieu of a DL, what else that works is.....? 160m at high noon......and 10m at midnight.?
On 40m, just find some SW AM broadcast station, and tune all you want.??
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Re: Bird Termaline load repair
In? lieu of a DL, what else that works is.....? 160m at high noon......and 10m at midnight.?
On 40m, just find some SW AM broadcast station, and tune all you want.??
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Re: Bird Termaline load repair
I gave up the oil loads years ago. Also supposed to use a special silicone oil which is not cheap.
I use air cooled loads, this one came out of the att ship to shore site in ocean gate New Jersey.
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On 2024-06-13 11:15, Brandon DX via groups.io wrote: Scott, I wonder if the resistor may have been replaced with one from a
contaminated load or a water load,
not knowing the history on it makes it a Sherlock Holmes case.
Measuring near 50 Ohms dc does show it has a good resistive element
though.
There are two types of elements used for load resistors like this, one
is a glass rod with the film deposited on it, the second is made of
bulk carbon.
I've seen the first type have a contaminated film on the surface over
the carbon that causes it to show increasing RL vs freq.
This occurs in water loads used for long periods with tap water.
Calcium or magnesium or something in the water binds to the surface of
the resistor and affects the performance vs freq. I knew first hand
this happening with a person using well water to cool a Bird load.
Not sure if old oil can contaminate a load though.
The remedy is to clean the resistor rod using alcohol followed by
baking soda in hot water.
If that fails then a new resistor might be available from Altronic
Research in Yellville AR. They make resistors.
GL Reid W6MTF
Links:
------
[1] /g/ham-amplifiers/message/40432
[2] /mt/106621215/8135091
[3] /g/ham-amplifiers/post
[4] /g/ham-amplifiers/editsub/8135091
[5] /g/ham-amplifiers/leave/12941173/8135091/773995006/xyzzy
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Re: Bird Termaline load repair
Scott, I wonder if the resistor may have been replaced with one from a contaminated load or a water load,
not knowing the history on it makes it a Sherlock Holmes case.?
Measuring near 50 Ohms dc does show it has a good resistive element though.?
There are two types of elements used for load resistors like this, one is a glass rod with the film deposited on it, the second is made of bulk carbon.
I've seen the first type have a contaminated film on the surface over the carbon that causes it to show increasing RL vs freq.
This occurs in water loads used for long periods with tap water.? Calcium or magnesium or something in the water binds to the surface of the resistor and affects the performance vs freq.? I knew first hand this happening with a person using well water to cool a Bird load.
Not sure if old oil can contaminate a load though.?
The remedy is to clean the resistor rod using alcohol followed by baking soda in hot water.??
?If that fails then a new resistor might be available from Altronic Research in Yellville AR. They make resistors.
GL? Reid? W6MTF
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Re: Bird Termaline load repair
It is an "exponentially tapered" section.? I can send a picture of the load assembly if that would help with suggestions.
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Re: Bird Termaline load repair
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Re: Bird Termaline load repair
The transition from "N" to the load should be a tapered "constant impedance" section.... not a flat plate which is fine to around 100mhz.
Don Roden?
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On 2024-06-11 3:47 pm, Dave w6de wrote:
The length of the coax between your dummy load and the test source is likely the culprit.? Try various lengths of coax.
?
73,
Dave, w6de
?
?
Peripherally related...
I have a new-to-me Bird 8890 load.? It's rated VSWR 1.1:1 to 1 GHz, but sweeps substantially worse, rising to nearly 3:1 at 435 MHz.
I've taken the load assembly out of the oil and there's no obvious physical damage.? The load does test 50.02 ohms at DC.
Any suggestions on what to try in order to get this bad boy back online?
Thanks,
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Re: Bird Termaline load repair
The length of the coax between your dummy load and the test source is likely the culprit.?
Try various lengths of coax.
?
73,
Dave, w6de
?
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From: [email protected]
<[email protected]> On Behalf Of Scott Townley via groups.io
Sent: 11 June, 2024 20:40
To: [email protected]
Subject: [ham-amplifiers] Bird Termaline load repair
?
Peripherally related...
I have a new-to-me Bird 8890 load.? It's rated VSWR 1.1:1 to 1 GHz, but sweeps substantially worse, rising to nearly 3:1 at 435 MHz.
I've taken the load assembly out of the oil and there's no obvious physical damage.? The load does test 50.02 ohms at DC.
Any suggestions on what to try in order to get this bad boy back online?
Thanks,
|
Bird Termaline load repair
Peripherally related...
I have a new-to-me Bird 8890 load.? It's rated VSWR 1.1:1 to 1 GHz, but sweeps substantially worse, rising to nearly 3:1 at 435 MHz.
I've taken the load assembly out of the oil and there's no obvious physical damage.? The load does test 50.02 ohms at DC.
Any suggestions on what to try in order to get this bad boy back online?
Thanks,
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Real 8k ultra with control box on the way
Have a factory made 8k ultra with spare plate transformer on the way. If not to screwed up I will fix and re sell. If beyond repair I will strip and part out.
Stay tuned to my YouTube channel under?
amp repair guy for updates.
I have been swamped with harbach orders and amp repairs.
Hope to be back on the 160-15 meter pa soon.?
?
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Re: WD7S lack of HV circuit ?
Yeah. You're right Jim.I hadn't thought it through that far and
you're right about the many handy applications. I use them a lot.
Alek VK6APK.
On 3/06/2024 12:53 am, Jim VE7RF wrote:
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Alek, I don't think the opto idea would work.? ?All the
resistors are in series, and regardless of value..... the
current is the same. (current in a series circuit is the same).?
IE: say 7500 vdc supply, and 25 x 100k @ 3 watt mof resistor is
series.... then add a 26th resistor (1666 ohms).? Current in the
string is just 3 ma.? ?3 ma x 1666 ohms = 5 vdc.
If an opto, whose input side operated on 5 vdc..... the same
opto will draw a lot more than 3 ma on it's input side, to
function.? ?Most are typ 10-20 ma on the input side.? ?Where is
that current going to come from??
I may well be missing something here.?
?
And for K6LPM, opto's are alive and well, used all the time.?
?The ODC-22's I use to key the sped up vac relays operate in
100u secs....and rls in 750u seconds.? They also have 5 kv
isolation between the input side and the output side.? ? They
came in a choice of? 9-15-24 vdc input sides? (with each of
those having a wide variance)? and a choice of either 60 vdc @ 3
amps ccs...or 200 vdc @ 1 amp for the sec side.? ?That's just 1
opto.? There are hundreds more to pick from.?
Switch transistors are a lot faster.? Like 3.6 microseconds,
300V rated at 500ma.? $1.85 from mouser.? ?My issue with switch
transistors is.... IF they ever failed shorted, then the entire
OCV? (open circuit voltage) is applied to the xcvr. IMO, the
huge isolation between input and output of the opto is a huge
advantage.? The input and output are totally isolated from each
other.? The opto part is just the laser / light firing a beam
from one side to the other.? There is no mechanical or
electrical connection between the input and output.? ?The output
side is essentially just a SPST-NO electronic switch.?
?
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Re: WD7S lack of HV circuit ?
Yep. I got a couple of those surplus boards many years ago and I use the couplers in lots of applications. Amplifier keying relay between radio and amp, bias cutoff resistor shorting relay in grounded grid amps, etc, etc.
They are so handy.
Alek VK6APK.
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On 2/06/2024 11:30 pm, Mike Sawyer via groups.io wrote: In another lifetime, we used OPTO22's for most of our control work where PLCs were involved. They used to make pre-printed circuit boards where you could get 5X, 10X or 20X units on a board. At a glance you could see which circuits were activated.
Mod-U-Lator,
Mike(y)/W3SLK
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Amp Guy Llc
Sent: Sunday, June 2, 2024 10:06 AM
To: [email protected]
Subject: Re: [ham-amplifiers] WD7S lack of HV circuit ?
My protection board for the 160-15 meter pa uses opto¡¯s. Nice thing is
they are super fast.
On 2024-06-01 20:42, K6LPM wrote:
Opto devices are pretty cool, but its like a technology that all of
sudded blew up overnight and as soon as it came on with so much
popularity it almost seems as if they dropped off with popularity with
designers and you see less and less used in practical designs... What
happened? It seems the Vactrol devices were an awesome device for
isolation and control puposes. Especially useful for audio switching,
especially hot switching. You seem them employed in high gain,
multichannel guitar amplifier preampligier channel switching schemes.
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Re: WD7S lack of HV circuit ?
Alek, I don't think the opto idea would work.? ?All the resistors are in series, and regardless of value..... the current is the same. (current in a series circuit is the same).?
IE: say 7500 vdc supply, and 25 x 100k @ 3 watt mof resistor is series.... then add a 26th resistor (1666 ohms).? Current in the string is just 3 ma.? ?3 ma x 1666 ohms = 5 vdc.
If an opto, whose input side operated on 5 vdc..... the same opto will draw a lot more than 3 ma on it's input side, to function.? ?Most are typ 10-20 ma on the input side.? ?Where is that current going to come from??
I may well be missing something here.?
?
And for K6LPM, opto's are alive and well, used all the time.? ?The ODC-22's I use to key the sped up vac relays operate in 100u secs....and rls in 750u seconds.? They also have 5 kv isolation between the input side and the output side.? ? They came in a choice of? 9-15-24 vdc input sides? (with each of those having a wide variance)? and a choice of either 60 vdc @ 3 amps ccs...or 200 vdc @ 1 amp for the sec side.? ?That's just 1 opto.? There are hundreds more to pick from.?
Switch transistors are a lot faster.? Like 3.6 microseconds, 300V rated at 500ma.? $1.85 from mouser.? ?My issue with switch transistors is.... IF they ever failed shorted, then the entire OCV? (open circuit voltage) is applied to the xcvr. IMO, the huge isolation between input and output of the opto is a huge advantage.? The input and output are totally isolated from each other.? The opto part is just the laser / light firing a beam from one side to the other.? There is no mechanical or electrical connection between the input and output.? ?The output side is essentially just a SPST-NO electronic switch.?
?
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Re: WD7S lack of HV circuit ?
In another lifetime, we used OPTO22's for most of our control work where PLCs were involved. They used to make pre-printed circuit boards where you could get 5X, 10X or 20X units on a board. At a glance you could see which circuits were activated.
Mod-U-Lator,
Mike(y)/W3SLK
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Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Amp Guy Llc Sent: Sunday, June 2, 2024 10:06 AM To: [email protected]Subject: Re: [ham-amplifiers] WD7S lack of HV circuit ? My protection board for the 160-15 meter pa uses opto¡¯s. Nice thing is they are super fast. On 2024-06-01 20:42, K6LPM wrote: Opto devices are pretty cool, but its like a technology that all of
sudded blew up overnight and as soon as it came on with so much
popularity it almost seems as if they dropped off with popularity with
designers and you see less and less used in practical designs... What
happened? It seems the Vactrol devices were an awesome device for
isolation and control puposes. Especially useful for audio switching,
especially hot switching. You seem them employed in high gain,
multichannel guitar amplifier preampligier channel switching schemes.
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Re: WD7S lack of HV circuit ?
Opto devices are pretty cool, but its like a technology that all of sudded blew up overnight and as soon as it came on with so much popularity it almost seems as if they dropped off with popularity with designers and you see less and less used in practical designs... What happened? It seems the Vactrol devices were an awesome device for isolation and control puposes. Especially useful for audio switching, especially hot switching. You seem them employed in high gain, multichannel guitar amplifier preampligier channel switching schemes.?
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Re: WD7S lack of HV circuit ?
This is for when the HV fuse in the B+? opens up = zero B+.? ? ?With no B+...and drive applied, you will peg the grid current meter.? A grid over current would achieve the same result, shut it down....like open off key line etc.
I came up with a unique, dead simple method for grid over current... dunno why I didn't think of it before, like 25 yrs ago....duh.? For now, it will be shrouded in complete mystery...till? I prove the concept.
Never thought of an opto isolator across the bottom resistor. (input side of the opto).? I will work it out on paper and see if it's doable.??
Jim
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Re: WD7S lack of HV circuit ?
My first thought was that this would be easy to set up with a
opto relay across the bottom resistor but on second thoughts, It
might be a bit more challenging because you have the bleed down of
the filter caps to contend with, on the DC side of the HV supply,
so there would be a substantial time delay in the tripping off.
The resistor voltage divider would need to be on the secondary
side of the transformer, before the rectifier and that's where it
gets tricky for a boy with a brain like mine.
Good luck, Alek VK6APK.
On 31/05/2024 10:01 pm, Jim VE7RF
wrote:
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WD7S,
on one of his boards he sold, was made to shut things down in
the event of loss of B+.
If
I remember?correctly, it resembled a mess of series resistors,
like you would use to meter HV, (without the meter), and an
extra smaller value resistor, in series at the cold end.? The V
drop across the small value resistor was like 5-7 vdc.... and
was applied to the rest of the circuit.
When
the B+ dropped below a given threshold, the circuit tripped, and
kicked the amp offline...like opening off the keyline etc.? I
think it used a spt, or dpdy mech relay..that was always
operated, with B+? turned on.? I think the coil was opened off
when the circuit tripped.
I can't find?the?original schematic for this board anywhere.?
Does anybody have any info on it ??
Jim? VE7RF
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WD7S lack of HV circuit ?
WD7S, on one of his boards he sold, was made to shut things down in the event of loss of B+.If I remember?correctly, it resembled a mess of series resistors, like you would use to meter HV, (without the meter), and an extra smaller value resistor, in series at the cold end.? The V drop across the small value resistor was like 5-7 vdc.... and was applied to the rest of the circuit.When the B+ dropped below a given threshold, the circuit tripped, and kicked the amp offline...like opening off the keyline etc.? I think it used a spt, or dpdy mech relay..that was always operated, with B+? turned on.? I think the coil was opened off when the circuit tripped.
I can't find?the?original schematic for this board anywhere.?
Does anybody have any info on it ??
Jim? VE7RF
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Bob
Brandon DX
K6LPM