Mike ,Thank you wonderful tip, I've just finished a project a Frequency Counter, I've added one of these small amps to it and made it switchable, that was a fantastic video a great help thank you for one of your pearls of wisdom.Paul de M0BSW in the radio shack for the bewildered.
Those are very cool. I have to get me another one due to sitting a power supply on top of mine and breaking the board in several pieces. Years ago we built our own and were powered through the frequency counter cable. But these are cheaper than building them now.
+The Radio Shop Yeah the price is so cheap it's ridiculous. I have the big bench lab amplifier which even I couldn't afford to buy brand new and you can also get small amplifier modules like this from mini-circuits. The mini-circuits ones are super high quality but come at a premium price to. For something like this though where you just need to amplify a signal a little for a frequency counter these cheap little amplifier modules are hard to beat.
These amplifiers were originally designed for Software Defined Radio. They are very wide banded, high gain and low noise. I do a lot of SDR and I've found that the shielded versions of these amps are even less noisy, but the lower noise factor probably won't make much of a difference in this application. If someone is looking for one, a good search term would be "SDR amplifier". I also have a laser cutter and made acrylic covers for mine to eliminate any chance of the circuit board touching anything on my bench. Good video. Thanks!
I picked up a couple of those a few months ago, I haven't played with them yet, I intend to put one in a box with BNC's, will replace my home build amp.
I THINK that may be a MMIC not a single transistor since there didn't appear to be any components around it for biasing, coupling etc., maybe a MAR-6 or something similar. Amazing how much easier these cheap little functional modules make life nowadays! TNX for the tip Mike.
Hi Mike! I don't have too many CB's cross my bench. (I mostly work on commercial and ham radio gear.) I keep hearing you talk about the adhesive that Cobra uses which corrodes everything around it. I finally had one of them hit my bench today. It's a Cobra 18 Plus. That stuff is nasty!!! I spent a while replacing circuit board jumpers and a few components before I could even get to the original problem. The radio has no TX or RX or channel indication. I touched up all of the connections between the main board and display board. (That was a dumb way to connect two boards.) The problem still exists, but now I get some channel segments to light up when pressing the main PCB around the PLL section. I was tired and closed shop for the night. I'll be back into it tomorrow, chasing bad solder joints. I can now understand how much you hate that adhesive. :-)
ahh the old Uniden IF circuit problem! gotta make sure your 1K tone is accurate if you can't measure those directly! thanks for this tip Mike, i just bought one so i have more freq counter options when doing oscillators. looked at buying some solder-on female BNC's, but they were more expensive than the adapters.
loosecannonradios - I just bought a few packages of these PCB mount BNC connectors from Amazon. Here's the link: www.amazon.com/gp/product/B072WQZHLD/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Thanks Mike! This is very good info. I use Auburn's P-20A probe. Had I known about this it sure would have save me some money, but it comes in handy now and then with my SA.
Roy Mercer Actually something like this is a perfect match for that probe. The probe your talking about is a 20db attenuation probe so the signal comming out of it is 20db smaller than it is at the tip. Attach that probe to this with its 30db amplification and the net result would be a 10db amplification over that sampled at the tip of the probe.
Yes sir. I ordered two of these amplifiers over the weekend. I had never thought to use a scope probe for the freq. counter. I can't believe over the years I never thought to of this!
I love my old Tektronix 2432A, as I use its Ch 2 output on the rear panel to drive the counter, so you use the scope as normal and view the waveform, and a buffered and amplified output is fed to the counter, unfortunately that scope is slowly dying and I have to keep on fixing it!
If the amplifier input is 1 meg or more, the probe attenuates by a factor of 10 or less. If it is 50 ohm, the probe attenuates by a factor of 180,000. The gain of 30 dB (i.e. about 30x) pales with that. I don’t think you get oscilloscope type input impedances on cheap amplifiers that can do 2 GHz. Typically I would expect 50 ohm, but what your demonstration with the spectrum analyzer seems to indicate is net gain. Hmmm? The other issue is, the counter adjustment knob likely is not sensitivity. It probably is trigger (comparison) level. At least all HP counters that I have dealt with used that approach. The least signal detection is when you have the knob set to zero. Maximum right setting represents the highest positive voltage in DC coupling and maximum amplitude in AC coupling. However, in the old units, the trigger point (reference level) often drifts. Needs calibration to restore the proper zero.
your calculation is off, the attenuation of a scope probe for a 75 ohm input is 20db in the times 10 setting. The amplifier is perfectly fine. Moreover, 30db is a times 1000 amplification.
The sensitivity will increase on the counter when the resolution is decreased, so thats the tradeoff. An amp can be built using (2) n2222 transistors and a couple of resistors and (2) .1 caps. By buying these parts in bulk, you could literally built 50 amps for the price of 2 of those...... Schematics for this are all over the net
Mike, I would really like to have you repair my father's old Roadtalker. I let someone who said they could repair it "repair" it. Now it's worse than before. He seemed like he knew what he was doing. Should have known better. I have a second one he used as a "parts" radio.
Good advice Mike. Have to try that. Some analog Tektronix scoops have a analog amplifier on the back. You can hook up counter to it. You see on the scoop the trace and the frequency, amplified by the Tek, on your counter. But your solution can be used for all equipment. How is the electronic course coming? 73's Henk
Hey Mike!! How are you doing? All is well I hope! A quick question if I may: You said, in a previous video, that you're fine with us re-capping our own radios if we're handy with a soldering iron. Is there ever a case for using caps of a different value other than that wich came stock with the radio? I know that when changing caps on an electric guitar's tone pots, different values will affect the guutar's tone. Should we leave the values "stock", or should/could we go with a different value?! I'm sorry if this seems like a "newbie" question, but if I don't ask, I won't know!! Thanks in advance, your fan: Norman
Pretty much anything cheap consumer electronics I work on I increase the voltage rating on the caps when I replace them. As for the value, unless you know what your doing it's best to stick with the factory value. In certain circuits it can adversely effect the radios performance/functionality if it doesn't have the correct value. It's safe to increase the value of the filter caps on the power rails.
MikesRadioRepair: Thanks for the quick reply!! You da man!! I have an RCA co-pilot 14T302 SSB radio. As far as I can tell, it was made in 1978-ish, and probably due for a re-capping & alignment. I can try the re-capping, but I don't have the equipment for an alignment. Any tips for a CBer from the 70's? I'd love to do as much work myself, IF I can!! I know enough to know that I don't know enough!! I just have to figure out why my power supply is putting out 26.8 volts instead of 13.8 volts!! Again, thanks very much for all your help & advice!! Your fan, Norman.
+Mister Hat LOL, it's only mismatched by 8,999,950 ohms. :-) In the 10X position it adds a 9 Meg resistor in circuit. It bumps up the impedance to prevent loading down circuits but really doesn't effect it when using it in this situation. We don't care about amplitude accuracy, only frequency accuracy in this case.
Defpom. Very true. But the voltage divider effect attenuates the signal by over 100dB, instead of the 20dB that would be from just using the probe. Therefore adding the amplifier would net 50dB less signal into a 1 meg input on a counter.
HI mike I'm new to your channel and getting back to cb's after getting out of the trucking industry in 2008 was wondering if you sell tuned out radios thanks
Your videos are helpful for many people. I can't watch longer than several minutes because of the constant extraneous dialog. You would be first class if you would stay focussed on the point .
You are a truly helpful person to numberous RF hobbies Mike. Thanks for your thoughtful videos to help so many folks. Double Thumbs Up to you.
Mike ,Thank you wonderful tip, I've just finished a project a Frequency Counter, I've added one of these small amps to it and made it switchable, that was a fantastic video a great help thank you for one of your pearls of wisdom.Paul de M0BSW in the radio shack for the bewildered.
Those are very cool. I have to get me another one due to sitting a power supply on top of mine and breaking the board in several pieces. Years ago we built our own and were powered through the frequency counter cable. But these are cheaper than building them now.
+The Radio Shop
Yeah the price is so cheap it's ridiculous. I have the big bench lab amplifier which even I couldn't afford to buy brand new and you can also get small amplifier modules like this from mini-circuits. The mini-circuits ones are super high quality but come at a premium price to. For something like this though where you just need to amplify a signal a little for a frequency counter these cheap little amplifier modules are hard to beat.
These amplifiers were originally designed for Software Defined Radio. They are very wide banded, high gain and low noise. I do a lot of SDR and I've found that the shielded versions of these amps are even less noisy, but the lower noise factor probably won't make much of a difference in this application. If someone is looking for one, a good search term would be "SDR amplifier". I also have a laser cutter and made acrylic covers for mine to eliminate any chance of the circuit board touching anything on my bench. Good video. Thanks!
I picked up a couple of those a few months ago, I haven't played with them yet, I intend to put one in a box with BNC's, will replace my home build amp.
Thanks Mike! Learning so much from your videos helping keep my old CB's running. Keep up the great work.
Thanks for the great tip.
I just ordered one with the two sma-bnc adapters. Cost was just under $10.00
Thank you now I know why my same did not work it was advertising as usb +5 volts would not work. Back to the drawing board
I THINK that may be a MMIC not a single transistor since there didn't appear to be any components around it for biasing, coupling etc., maybe a MAR-6 or something similar. Amazing how much easier these cheap little functional modules make life nowadays! TNX for the tip Mike.
Hi Mike! I don't have too many CB's cross my bench. (I mostly work on commercial and ham radio gear.) I keep hearing you talk about the adhesive that Cobra uses which corrodes everything around it. I finally had one of them hit my bench today. It's a Cobra 18 Plus. That stuff is nasty!!! I spent a while replacing circuit board jumpers and a few components before I could even get to the original problem. The radio has no TX or RX or channel indication. I touched up all of the connections between the main board and display board. (That was a dumb way to connect two boards.) The problem still exists, but now I get some channel segments to light up when pressing the main PCB around the PLL section. I was tired and closed shop for the night. I'll be back into it tomorrow, chasing bad solder joints. I can now understand how much you hate that adhesive. :-)
ahh the old Uniden IF circuit problem! gotta make sure your 1K tone is accurate if you can't measure those directly!
thanks for this tip Mike, i just bought one so i have more freq counter options when doing oscillators.
looked at buying some solder-on female BNC's, but they were more expensive than the adapters.
loosecannonradios - I just bought a few packages of these PCB mount BNC connectors from Amazon. Here's the link: www.amazon.com/gp/product/B072WQZHLD/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
Scope probe in the x10 position has a 20db power attenuation. that is why a broadband ~20db amplifier helps raising the signal.
You nailed it, Mike! Thanks!
Thanks Mike! This is very good info. I use Auburn's P-20A probe. Had I known about this it sure would have save me some money, but it comes in handy now and then with my SA.
Roy Mercer
Actually something like this is a perfect match for that probe. The probe your talking about is a 20db attenuation probe so the signal comming out of it is 20db smaller than it is at the tip. Attach that probe to this with its 30db amplification and the net result would be a 10db amplification over that sampled at the tip of the probe.
Yes sir. I ordered two of these amplifiers over the weekend. I had never thought to use a scope probe for the freq. counter. I can't believe over the years I never thought to of this!
Mike, I see that you have a Schlumberger Stabilock 4040. I worked for that company in the service department and repaired them.
I love my old Tektronix 2432A, as I use its Ch 2 output on the rear panel to drive the counter, so you use the scope as normal and view the waveform, and a buffered and amplified output is fed to the counter, unfortunately that scope is slowly dying and I have to keep on fixing it!
Great Vid. as usual Mike. Thanks great idea.
If the amplifier input is 1 meg or more, the probe attenuates by a factor of 10 or less. If it is 50 ohm, the probe attenuates by a factor of 180,000. The gain of 30 dB (i.e. about 30x) pales with that. I don’t think you get oscilloscope type input impedances on cheap amplifiers that can do 2 GHz. Typically I would expect 50 ohm, but what your demonstration with the spectrum analyzer seems to indicate is net gain. Hmmm?
The other issue is, the counter adjustment knob likely is not sensitivity. It probably is trigger (comparison) level. At least all HP counters that I have dealt with used that approach. The least signal detection is when you have the knob set to zero. Maximum right setting represents the highest positive voltage in DC coupling and maximum amplitude in AC coupling. However, in the old units, the trigger point (reference level) often drifts. Needs calibration to restore the proper zero.
your calculation is off, the attenuation of a scope probe for a 75 ohm input is 20db in the times 10 setting. The amplifier is perfectly fine. Moreover, 30db is a times 1000 amplification.
The sensitivity will increase on the counter when the resolution is decreased, so thats the tradeoff.
An amp can be built using (2) n2222 transistors and a couple of resistors and (2) .1 caps. By buying these parts in bulk, you could literally built 50 amps for the price of 2 of those......
Schematics for this are all over the net
Mike, I would really like to have you repair my father's old Roadtalker. I let someone who said they could repair it "repair" it. Now it's worse than before. He seemed like he knew what he was doing. Should have known better. I have a second one he used as a "parts" radio.
Good advice Mike. Have to try that. Some analog Tektronix scoops have a analog amplifier on the back. You can hook up counter to it. You see on the scoop the trace and the frequency, amplified by the Tek, on your counter. But your solution can be used for all equipment. How is the electronic course coming? 73's Henk
Are you using the amplifier for the counter only. What is the noise figure of the amp at the frequency you are using it ?
Hey Mike!! How are you doing?
All is well I hope! A quick question
if I may: You said, in a previous
video, that you're fine with us
re-capping our own radios if we're
handy with a soldering iron.
Is there ever a case for using caps
of a different value other than that
wich came stock with the radio?
I know that when changing caps
on an electric guitar's tone pots,
different values will affect the
guutar's tone. Should we leave
the values "stock", or should/could
we go with a different value?!
I'm sorry if this seems like a "newbie" question, but if I don't ask, I won't know!!
Thanks in advance, your fan:
Norman
Pretty much anything cheap consumer electronics I work on I increase the voltage rating on the caps when I replace them. As for the value, unless you know what your doing it's best to stick with the factory value. In certain circuits it can adversely effect the radios performance/functionality if it doesn't have the correct value. It's safe to increase the value of the filter caps on the power rails.
MikesRadioRepair: Thanks for the quick reply!! You da man!! I have an RCA co-pilot 14T302 SSB radio.
As far as I can tell, it was made in 1978-ish, and probably due for a
re-capping & alignment. I can try
the re-capping, but I don't have the equipment for an alignment. Any
tips for a CBer from the 70's? I'd
love to do as much work myself,
IF I can!! I know enough to know
that I don't know enough!! I just
have to figure out why my power supply is putting out 26.8 volts
instead of 13.8 volts!!
Again, thanks very much for all
your help & advice!!
Your fan, Norman.
impedance matching on input and output needed ?
Mike when using your spectrum analyzer for this task do use a attenuator? If so what size? Thanks.
How well does the 50 ohm impedance work with a x10 probe? Seems like a huge mismatch.
+Mister Hat
LOL, it's only mismatched by 8,999,950 ohms. :-) In the 10X position it adds a 9 Meg resistor in circuit. It bumps up the impedance to prevent loading down circuits but really doesn't effect it when using it in this situation. We don't care about amplitude accuracy, only frequency accuracy in this case.
I understand about not caring about accuracy, but that mismatch should be greater than the 30dB gain of the amplifier and defeat the purpose.
The test points aren't 50 Ohm anyway, only the transmission line is, you want a very high resistance to reduce the loading, as Mike said.
Defpom. Very true. But the voltage divider effect attenuates the signal by over 100dB, instead of the 20dB that would be from just using the probe. Therefore adding the amplifier would net 50dB less signal into a 1 meg input on a counter.
Does it have enough gain to boost a VFO signal to the mixer on a Johnson Messenger 223 tube CB? I have one with aged crystals and I want to add a VFO.
+scott king
No, it's maximum output is only +10dbm. Contact Chris at Nomad Radios. He makes a buffer/amplifier board for just this purpose.
HI mike I'm new to your channel and getting back to cb's after getting out of the trucking industry in 2008 was wondering if you sell tuned out radios thanks
Tay trak
I don't sell anything, repairs only. Sorry.
Your oscilloscope doesn't have an ampliified output?
That is a cool fix, on a budget. Thankyou, I use what you call export RADIO. SORRY, 😭😭😭😭😭😭😭 MIKE.
Haven't seen a General radiotelephone on your videos, how about a MC-11
how would I get ahold of you to send a radio to you.
Super...
can you add a link
Your videos are helpful for many people. I can't watch longer than several minutes because of the constant extraneous dialog. You would be first class if you would stay focussed on the point .