Kage
Mudduck
Posts: 11
|
Post by Kage on Sept 14, 2017 5:41:26 GMT -5
Hello, new here to this forum. I run a similar message forum but it's more related to pirate radio on shortwave and broadcast AM/FM along with the technically geared types that like to do their own DIY projects. Been in CB radio since I was a kid and felt the itch to play around with the 11m band again. Got my hands on an older 23 channel Teaberry Five by Five and modified it heavily over the last few years. One thing I have been wanting to do is attach a VFO so I can cover the full 40 channels, and the freeband channels along with amateur 10m which the latter will be nice when licensed. Yeah lazy on that one because there are no VE's near me  Yes I know the legality of using a VFO with CB radios, it's legal to use for reception so for now lets just say that's what I am using it for. I don't mean to cross-link to another proboards forum if that's against rules but I wrote up a long thread about the project on my own forum with plenty of pictures kind of like a blog so it would be redundant to post the same stuff here.. darkliferadio.proboards.com/thread/891/high-stability-radio-project-blogHere is what the final design looks like sitting next to the old Uniden Teaberry...  I took a lot of time studying how the Siltronix VFO works along with the PAL. The PAL is obviously better because it mixes a lower VFO frequency with a crystal oscillator for stability. Getting my VFO to work with little drift was no easy task but the permeability tuned oscillator plus quality capacitors made it come to the stability of the PAL if not better. I get around +-2hz per minute drift, plenty good for AM and SSB. I may improve on this eventually but I doubt I can get it down to <8-10Hz per minute in high temperature changes outside of ambient house temp. That's okay though because I plan to use it indoors only. Been hearing people talk on 27.505AM lately if I recall correctly. I have the parts now to stick up a EFHW antenna I am making out of 17' conduit pipe and a piece of PVC for a tower insulator. Hope this little project pays off and is able to make the range to them with my barefoot radio, VFO, and half wave vertical once constructed. Hope I am welcome here. I love older radios, may be 32 y/o but always been a tube guy and DIY type that loves designing and repairing electronics, so.. Hi! |
|
Sandbagger
Administrator/The Boss 
Posts: 6,247 
|
Post by Sandbagger on Sept 14, 2017 7:05:55 GMT -5
Hello, new here to this forum. I run a similar message forum but it's more related to pirate radio on shortwave and broadcast AM/FM along with the technically geared types that like to do their own DIY projects. Been in CB radio since I was a kid and felt the itch to play around with the 11m band again. Got my hands on an older 23 channel Teaberry Five by Five and modified it heavily over the last few years. One thing I have been wanting to do is attach a VFO so I can cover the full 40 channels, and the freeband channels along with amateur 10m which the latter will be nice when licensed. Yeah lazy on that one because there are no VE's near me Yes I know the legality of using a VFO with CB radios, it's legal to use for reception so for now lets just say that's what I am using it for. I don't mean to cross-link to another proboards forum if that's against rules but I wrote up a long thread about the project on my own forum with plenty of pictures kind of like a blog so it would be redundant to post the same stuff here.. darkliferadio.proboards.com/thread/891/high-stability-radio-project-blogHere is what the final design looks like sitting next to the old Uniden Teaberry... I took a lot of time studying how the Siltronix VFO works along with the PAL. The PAL is obviously better because it mixes a lower VFO frequency with a crystal oscillator for stability. Getting my VFO to work with little drift was no easy task but the permeability tuned oscillator plus quality capacitors made it come to the stability of the PAL if not better. I get around +-2hz per minute drift, plenty good for AM and SSB. I may improve on this eventually but I doubt I can get it down to <8-10Hz per minute in high temperature changes outside of ambient house temp. That's okay though because I plan to use it indoors only. Been hearing people talk on 27.505AM lately if I recall correctly. I have the parts now to stick up a EFHW antenna I am making out of 17' conduit pipe and a piece of PVC for a tower insulator. Hope this little project pays off and is able to make the range to them with my barefoot radio, VFO, and half wave vertical once constructed. Hope I am welcome here. I love older radios, may be 32 y/o but always been a tube guy and DIY type that loves designing and repairing electronics, so.. Hi! Welcome to the forum! Speaking for myself, I always enjoy having members who like to tinker with radio, especially vintage radios. There are a lot of forums and Facebook pages dedicated to various aspects of more modern CB radio. Here, we specialize in vintage radios, antennas, operators, amplifiers and projects. So your VFO project fits right in. I am curious why you decided to go "old school" analog VFO and not try either a PLL circuit or a direct frequency generator, as these seem to be more stable than a VFO. I like your final construction. Looks almost commercial. It's also nice that we have frequency counters that can plug right in. Sure beats having to create an analog dial and linearizing it through its range. Good luck with the project. Hope to hear more about it. |
|
Kage
Mudduck
Posts: 11
|
Post by Kage on Sept 15, 2017 8:23:46 GMT -5
I am curious why you decided to go "old school" analog VFO and not try either a PLL circuit or a direct frequency generator, as these seem to be more stable than a VFO. I like your final construction. Looks almost commercial. It's also nice that we have frequency counters that can plug right in. Sure beats having to create an analog dial and linearizing it through its range. Good luck with the project. Hope to hear more about it. I went with the LC type VFO for simplicity, plus being as it's a Vackar type oscillator and tuned using the coil instead of a variable capacitor the stability is very good with a large frequency span without having to use a switch to change band ranges. The other reason is that modern direct digital synthesizers often have noise on their output which can cause issues reception noise, birdies, transmit spurs and so on. It takes a bit to clean up that signal to be useful whereas a simple transistor oscillator can be made to have an extremely clean output and low phase noise. PLL circuits are nice but once again add complexity. I know there are huff&puff stabilizers that can be added on so that's always a future option but may be overkill for this use. I guess the only thing I wanted digital in this project was the frequency counter for practicality, after all I am attaching this to older CB radios so it just feels right using something less modern to pair with them. Thanks for the input and warm welcome  |
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 15, 2017 11:20:14 GMT -5
I am curious why you decided to go "old school" analog VFO and not try either a PLL circuit or a direct frequency generator, as these seem to be more stable than a VFO. I like your final construction. Looks almost commercial. It's also nice that we have frequency counters that can plug right in. Sure beats having to create an analog dial and linearizing it through its range. Good luck with the project. Hope to hear more about it. .......I guess the only thing I wanted digital in this project was the frequency counter for practicality, after all I am attaching this to older CB radios so it just feels right using something less modern to pair with them. BEST answer right there. |
|
|
|
Post by 2600 on Oct 12, 2017 22:33:00 GMT -5
Very cool project.
Has a high appeal to an "analog retentive" like me.
I'm still pursuing a DDS project idea, when time permits.
Rock on!
And, 73
|
|
|
|
Post by grimace on Oct 18, 2017 23:54:26 GMT -5
have you had any problems with the frq count on the vfo I heard the the voltage regulator is to small and burns out
|
|
|
|
Post by 2600 on Oct 21, 2017 11:25:39 GMT -5
You have to reduce the input voltage to those counters to 8 or 9 Volts, max. If you power it from the radio's main 14-Volt DC supply, the counter's internal regulator may overheat. It should safely shut itself down until you power it off and let it cool off.
We install a 8-Volt 3-terminal regulator in the Siltronix VFOs where we use those. Haven't had a problem since we started doing that.
73
|
|
Kage
Mudduck
Posts: 11
|
Post by Kage on Oct 28, 2017 10:13:14 GMT -5
have you had any problems with the frq count on the vfo I heard the the voltage regulator is to small and burns out I also heard about that being an issue. Even though originally I was running the full 13.8v to the counter I decided it would be smart to play safe so I added a 7808 voltage regulator to it. For people who don't have an 8 volt regulator I'd be willing to bet gluing on a chunk of metal to the onboard regulator would help keep it cool. The counter needs to stay cool anyways being as it's inside the same box as the VFO. Any fast and large temperature variations would mess up the VFOs stability, even with temperature compensating capacitors and a distance you'd be surprised how little it takes to throw things off if a regulator gets warm fast in the same unit. I honestly find it hard to believe that the onboard voltage regulator for the counter would burn out given I have never felt it get warm. Makes me wonder if people are giving it more than the 15 volts the specs say is the maximum? I keep mine on lowest LED brightness though, I find the higher brightness levels to be an eye killer with that bright blue. Either way no issue luckily. I did have to play with the one potentiometer on the counter that sets where it triggers and seems to adjust its sensitivity. I think that was slightly off from the factory. |
|
|
|
Post by bobcat4109 on Mar 19, 2019 13:51:17 GMT -5
I don't know whether you are still around or not but looking at your design, made me want to ask (about that frequency counter module).
I have the 8 digit one and, cheapskate that I am, had visions of using it more or less as a bench counter. The one thing that I am uncertain of is the sensitivity. I think it says that in the low range it is around 60mv p-p. In your opinion do you think that this would work well enough to use probing around inside a radio as it is? If not, would a high frequency preamp help to insure it??
Thanks in advance if you should see this!
Bob
|
|
Kage
Mudduck
Posts: 11
|
Post by Kage on Apr 20, 2019 2:28:09 GMT -5
I don't know whether you are still around or not but looking at your design, made me want to ask (about that frequency counter module). I have the 8 digit one and, cheapskate that I am, had visions of using it more or less as a bench counter. The one thing that I am uncertain of is the sensitivity. I think it says that in the low range it is around 60mv p-p. In your opinion do you think that this would work well enough to use probing around inside a radio as it is? If not, would a high frequency preamp help to insure it?? Thanks in advance if you should see this! Bob Yeah I am still around. Been a while since visiting. If I were to use one as a bench counter I would certainly add a few things. For one at bare minimum diode limiter input protection, like 1N4148 diodes back to back in parallel to limit AC input to <0.7v and a few hundred ohm resistor before them for current regulation to act as a protection circuit. I forget what the sensitivity is of these counters but it sure couldn't hurt to add a JFET front end to it if you want it to sense weak signals or even off a sniffer antenna. It certainly would be fairly simple to add, and the diodes ahead of it would protect the JFET gate from static and large voltage swings. Eventually I might do something similar and get back to posting a circuit idea. Sorry for the long away time, life and things..
|
|
|
|
Post by bobcat4109 on Apr 22, 2019 8:58:27 GMT -5
No problem at all! Pleased to see your response and thank you for it!
|
|
