{combing all future thoughts and ideas into one thread for this topic}
Yeah dumb title for a goofy topic considering what I have to work with..
Teaberry Five-by-Five 23 channel (modded to 24 channel by enabling the DOT on the dial between 1 and 23) 50 feet of RG-6/u CATV/Satellite 75ohm cable Homemade dipole (may possibly change) Homemade air balun, aka UGLY balun Modified modulation to utilize heavier iron for high quality AM
So far I modded the radio itself to cover channel 24. Yes I am that cheap. I could just buy a 5$ CB that covers all 40 channels but why not lol. Part of the goal here is to make the most out of the worst case scenario and see what I learn and accomplish along the way. It's actually quite easy to mod a 23 channel CB to cover 24 on that * between 23 and 1. There is a simple notch out of the channel dial but the internal crystals do allow for the channel, but back then that channel was not for CB use. People use to use channel 24 as a private channel outside of the CB band before it became a real channel, and this also explains the strange CB radio channel frequencies not being linear from 1 through 40 in case you ever wondered.
75 ohm coax you say? Once again why not? I find that I get about the same feed-line insertion loss with RG6/U 2200MHz satellite cable as I do my fat RG8/U 50ohm that is currently in use for FM broadcasting.
Playing with a simple dipole I am noticing an odd effect and not sure if this is related to the air balun or not but I cut two pieces of wire for 102" for each side of the 11 meter dipole and find that the sweat spot for lowest SWR is actually about 3 to 5" less on each side. This does not matter if it's up in the air or low to the ground. I am worried that this may have something to do with power loss in the balun?
Contacts have been good today. I strung up the dipole at 30' vertically, partially slanted and made some local contacts as far as a few towns away, and this was with the mess of skip. People were amazed I could talk to them when they couldn't talk to their trucking friend down the road. So I must be doing something right.
I learned that 75 ohm coax works fine when pushing a 50 ohm radio into it but there is some slight SWR reflection even at the best. Some say the best case is 1.5 for SWR. I disagree however because there is one untapped feature of older radios and that is to simply tweak the tank output coils to agree with the 75 ohm load instead of what it was designed for. Anyone can do this with a proper SWR meter that can read a 75 ohm load and a 75ohm dummy load connected directly to the meter, the meter connected directly to the radio. Just peak the tank slugs until you get zilch on the meter for SWR then it will play fine with your new impedance. Just make sure the slugs you play with are the right ones. You can imagine this being like an old tube type transmitter with a load and tune coil. Solid state radios aren't much different, just double check the schematic so not to screw up unwanted coils.
I'd imagine the design of the radio can have more influence or less than others on this switchover. I also imagine the more forgiving older radios of yesteryear can work with 75 ohm cable w/o ANY modifications besides using a proper 75 ohm SWR meter instead of the common 50ohm type. (using a 50ohm SWR meter over a 75ohm coax will result in a 1.5 positive miscalculation in SWR, but not relative to actual performance)
Final notes for this current post:
I have learned that it's possible to split coax and literally resolder back together and use electric tape with out any loss at HF. Not a good idea and don't ask how I now know this, but it's not a water hose, it's not going to leak RF all over if you patch spots or pieces of coax together w/o RF connectors.
75 ohm RG6/U fits PL259 and SO239 connectors if you are patient and use some basic skills. The outside braid will not solder because of the type of metal, but luckily there is enough surface connectivity to not be an issue with basic RF connectors. There are tutorials online showing how to do this.
Vertical antenna polarization is good for local communication AND skip, but horizontal is almost only limited to skip. This comes from the fact that skipped signals tend to come down spinning polarization over distances whereas local communications is limited to specific polarizations of antennas, and being that most local CB users use vertical... well one must use vertical to communicate back.
People are using far too much length for current 1:1 baluns. I seen a few online docs showing to use 1/2+ wavelength or more in coax for ugly baluns. In fact his has me double guessing my own suggestions for FM broadcast telling people 1/2 wave is the length to use for a balun on a J-Pole which obviously isn't going to hurt, but may actually be a bit much. For CB or 10 meters I found the right amount of balun length is right around 7 feet at 4.5" diameter. This would actually be 1/4 wave length of coax. The hell if I know. I will research this more later. For now I used the specs the ARRL book said for 10 meters on CB and it works well.
Found out that a few of the crystals were slightly off frequency by as much as 1kHz so I added a hand selected capacitor in series with the offending crystals to pull the oscillator frequencies back to where they belong.
I suspect that many old 23 channel CB radios have this issue from aged crystals and even notice while listening to skip that many peoples radios cause beat frequencies with others on the same channel causing audible whistling of many tones from many radios not being spot on frequency. I would think with most people using PLL based radios today that it would be a thing of the past but maybe this is not the case?
Found out that all 23 channel radios run <4 watts. Most being from 3.2 to 3.8 watts. The reason being that when the FCC first licensed CB radios they had a rule stating that the radio could only run 5 watts of input power, or in other words 5 watts maximum power DC into the final RF transistor stage. This would result in an RF output that was 3.5 watts on average. When the FCC allowed 40 channel radios and phased out the 23 channel radios they rewrote the rule stating that radios could have a maximum RF output of 4 watts, instead of the 5 watt input DC rule. So this explains why 23 channel radios usually put out less power than 40 channel radios. It is not a flaw, they were designed with the rules of the time in mind.
Playing around with the RF stage of my radio I discovered a few things that could be modified to get a bit more wattage out without mangling the circuits. I won't go into great detail but a bit of reverse engineering and a tiny bit of rework on the RF stage let me get 5 watts out dead key and 20 watts fully modulated using the original RF transistor and driver. I left the original tuning tank and 54MHz rejection filter circuits alone besides making sure they were aligned properly. Using a beefier low loss modulation transformer also helped increase RF power and of course helps audio fidelity greatly on air and on receive.
One disturbing trend I see online is CB enthusiasts modifying their rigs to have positive modulation swing. This is idiotic if you ask me as it does nothing good for the signal except distort the audio. It is possible to have positive going modulation but requires proper negative modulation keep-alive circuits or special audio processing to avoid negative clipping which causes channel splatter and actually reduces signal strength. This is something no CB radio has built in circuits to handle so using positive carrier swing is a waste of time. I tuned my radio like the factory intended, zero carrier swing on full modulation which gives the best audio fidelity on air. Amazing how many people out there don't understand this basic fact when modifying their radio with those moronic swing kits or think splattering up and down half the channels is a good thing!
I have owned a lot of CB radios in my life but with the mods done to this one so far it has become my favorite for audio quality, receiver sensitivity and ability to be modified easily. Bummer it is only a 23 (24 counting blank channel mod) channel unit but next plan of mine is to add a VFO so I can tune the thing anywhere I want up and down 12 through 10 meters.
It's like that in the audio amp field as well ... go for the better numbers, who cares what it sounds like?
But a crystal that's 1KHz off? My guess is the hermetic sea is kaput and the crystal is physically contaminated to do that. If you have a spectrum analyzer, you can see if it's physicaly broken as there will be resonance spikes all over the place.
It's like that in the audio amp field as well ... go for the better numbers, who cares what it sounds like?
But a crystal that's 1KHz off? My guess is the hermetic sea is kaput and the crystal is physically contaminated to do that. If you have a spectrum analyzer, you can see if it's physicaly broken as there will be resonance spikes all over the place.
Cheers!
Oddly it was not the only crystal that had a similar issue. I took the same frequency crystal out of another radio in my junk pile just to see if it would work better and although it did work fine it was also ~600Hz off but in the opposite direction. I read online that this is quite common for old crystals that were used in CB radios. I am guessing that it could have been caused by heat exposure in hot vehicles or maybe even ice cold temps. Who knows, but the crystal does work and the oscillator driving it gives a clean sine output so pulling the crystal slightly to get it spot on with a capacitor worked just fine. The rest of the crystal bank were close enough to actual frequency to not be of issue.
Long needed update with some cool projects in the making
I gave up on most of the other radical antenna ideas and decided to go with an end fed dipole antenna. Lots of plans on the internet for these types of aerials including your generic J-Pole and the more fancy End Fed Half Wave Antenna or better known as EFHWA. The only real difference between those two antennas is that one is fed into a toroid transformer (EFHWA) and the other into a matching stub (J-Pole), other than that they are both 1/2 wave dipoles fed off their end rather than center.
Having no toroids around that would suit the job I opted for an old ferrite bar. Windings were found by trial and error. 9:1 ratio worked the best with 2 windings primary and 18 secondary for 27MHz. I moved the primary winding around to get the lowest SWR into a 4.7K Ohm load on the secondary as described how to do here... This allowed me to bypass the tuning capacitor altogether found in most EFHWA antenna designs.
Secondary coil only has one lead attached to the 1/2 wave wire, I opted to make a ground terminal just in case but have not needed to use it for any sort of counterpoise. Oddly this thing works off of only one side of the secondary winding with the other wire not connected to anything!
SWR is in the dirt. Won`t even budge my meter hardly. Going to say around 1.5 on highest if I put my hand near the antenna.
Best part of this type of antenna just like the J-Pole is that it only needs one support as it is bottom fed.
Transformer guts...
Mounted into a Sleep & Relax pill bottle... because now I can sleep and relax lol. Far left bolt is 1/2 wavelength wire aerial connection, bottom bolt is ground (not used currently), and right is the coax connector to radio.
Next up is a roger beep I made. Yeah noise toys can get annoying but I don`t blast mine to be a dick, I only use them when shooting skip so over the noise of other people really do know I am over and out. This is a two tone beep I made from scratch. The two tone idea circuit design is original by me (and if anyone copies the design please give credit where due) and works damn well with a high then low tone both nice sine wave tones and not chirpy sounding like some cheap roger beeps...
Really bad snapshot of the schematic, will update later... Transistors are either 2N3904 or 2N3906. the 4.7 is actually 4.7K. I forgot to draw the K lol. Relay I used was a 5 volt type and timing relies on 5 volts specific so the 7805 regulator is necessary.
The antenna really amazed me. I really think more people here should look into the EFHWA antenna. They work almost too well. I was amazed when first design I made fired off perfectly as good as a generic center fed dipole. Definitely an antenna people should rediscover!
Just in case anyone is curious about the schematic since I think it is really cool I figured out how to make a two solid tone roger beep like this...
First transistor on the far left is keying circuit. When pressing PTT it will instantly engage the relay switching the radio from RX to TX. Discharge is done through the capacitor in parallel with the PTT button. Higher uF value, longer beep and release time.
Middle two PNP transistors are timer circuits. They engage in order from top to bottom. They cut out the oscillator (far right transistor) until their voltage sensed by the PTT capacitor drops below a specific value. When the voltage drops below a specific level the top transistor enables the oscillator to play the higher roger tone. Soon after the bottom transistor times out and drags down resistance instantly on the oscillator to play the lower roger tone thus giving a single high tone beep then a single low tone beep then unkey of the radio. The dotted line with the switch is optional to engage either both tones or just only the single tone roger. I did not include this in my final design and opted for the 2 tone as permanent.
How things have changed. Roger Beeps when I was a younger fella got your coax cut!
Times really haven't changed that much LOL The reason they became so damn annoying is because locals started using them for regular contacts which was redundant considering everyone knew they were done talking. They can be useful for SSB or skip when there is a pileup and you are talking to someone specific. What I never understood is those people who use them all the time and have the tone louder than their own voice. That is just asking for it
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