This project has been the eternal prototype. Each successive version reveals yet another fatal flaw to fix.
It started out as a way to use roger beep boards that lack a relay in radios that require the mike to receive. You need a relay for that, since the mike was keeping the receive speaker switched off while the transmitter is keyed. A roger beep keeps the radio keyed after you release the mike. Without a relay you would get a deafening BEEP! every time you unkey. You don't need pics of a relay strapped inside the radio the way we started doing this. Strapping pin 2 to pin 4 in Uniden SSB CB radios with the 8719 PLL chip was necessary so the 5-pin mike would still work. Eventually the idiot light came on and we started swapping the mike socket for a 4-pin. Since we're only using pins 1,2 and 3 this just makes life easier since newer radios tend to use the 4-pin plug.
Back in 1979 when the 5-pin SSB CB radios first appeared, this flustered folks who wanted to know why they needed a mike with six wires. "What's wrong with the 4-wire D104 I'm using now" was the frequent question.
Never mind the details, but five just doesn't equal 4.
Eventually I got tired of manually installing a relay in a Cobra 2000, Washington, Madison etc radios. Decided to put it all on a pc board and save a lot of labor installing a Roger K or 5-tone or "bump-bump".
But this method had a problem. In most radios this would produce an annoying "POP!" when you release the mike. Wasted a lot of time looking for the source of this aggravation.
Then my idiot light came on. The pop was always there, but the speed with which your thumb comes off the mike button would keep the speaker switched off until the POP had died down.
Sure enough, if you slide your thumb off the mike button so that it pops out as fast as the spring will push it, you'll hear that POP. It was there all along.
So, the cure is to use two relays, and delay the one that switches on the speaker. Simple enough, a capacitor and diode will create this sequence.
Of course this is ugly, and way too shaky to use in a mobile radio, but it worked. Wa-hoo!
Just one problem fitting two relays on a pc board small enough to fit where it goes.
Yet another problem. Surfing for bargains, I found this relay at All Electronics and bought a batch. They just didn't hold together well at all.
Oops.
New solution, use a better-quality Omron relay.
This pic shows versions five and six. Turns out the fix has a problem. The audio current through the receive-side relay is more than it can handle. Radios that were used mobile would burn out the contacts in the receive relay and kill the receiver audio. Lasted longer in a base radio. Volume doesn't get turned as high.
Oops.
Can't get a relay rated for 3 Amps small enough to fit two of them. Decided to use a transistor to key the radio's transmit wire, and a single relay for the speaker.
At least it fits. Just one problem. Getting the layout right.
Not the end of the world. With trace cuts and a bodge wire it works as desired. Just can't sell a board with this kluge on it. Wouldn't be professional.
Besides, I installed the relay in half of them before discovering I had a trace underneath it that shouldn't even be there to begin with. It's the same trace that's on the solder side, just failed to see it.
Couldn't (wouldn't) very well remove those relays to cut this trace. Fixed the art errors, and ordered another batch.
So here is the revised board, going into a Philippines Cobra 148, first guinea pig for version 8. The 3-Amp relay had better dern well be big enough to last a while.
Yeah, the "P2" hole was empty in the previous pic. Pin 2 of the 5-pin socket connects to an axial RF choke with yellow sleeve on the leads. Wont'reach the board until it's bolted in place.
Works a treat, as the aussies would say. Yeah, version eight. Spared you the rest of the incremental learning experiences.
Maybe version eight is finally ready for prime time. But not before a few dozen of them get made.
Sounds easy.
73
It started out as a way to use roger beep boards that lack a relay in radios that require the mike to receive. You need a relay for that, since the mike was keeping the receive speaker switched off while the transmitter is keyed. A roger beep keeps the radio keyed after you release the mike. Without a relay you would get a deafening BEEP! every time you unkey. You don't need pics of a relay strapped inside the radio the way we started doing this. Strapping pin 2 to pin 4 in Uniden SSB CB radios with the 8719 PLL chip was necessary so the 5-pin mike would still work. Eventually the idiot light came on and we started swapping the mike socket for a 4-pin. Since we're only using pins 1,2 and 3 this just makes life easier since newer radios tend to use the 4-pin plug.
Back in 1979 when the 5-pin SSB CB radios first appeared, this flustered folks who wanted to know why they needed a mike with six wires. "What's wrong with the 4-wire D104 I'm using now" was the frequent question.
Never mind the details, but five just doesn't equal 4.
Eventually I got tired of manually installing a relay in a Cobra 2000, Washington, Madison etc radios. Decided to put it all on a pc board and save a lot of labor installing a Roger K or 5-tone or "bump-bump".
But this method had a problem. In most radios this would produce an annoying "POP!" when you release the mike. Wasted a lot of time looking for the source of this aggravation.
Then my idiot light came on. The pop was always there, but the speed with which your thumb comes off the mike button would keep the speaker switched off until the POP had died down.
Sure enough, if you slide your thumb off the mike button so that it pops out as fast as the spring will push it, you'll hear that POP. It was there all along.
So, the cure is to use two relays, and delay the one that switches on the speaker. Simple enough, a capacitor and diode will create this sequence.
Of course this is ugly, and way too shaky to use in a mobile radio, but it worked. Wa-hoo!
Just one problem fitting two relays on a pc board small enough to fit where it goes.
Yet another problem. Surfing for bargains, I found this relay at All Electronics and bought a batch. They just didn't hold together well at all.
Oops.
New solution, use a better-quality Omron relay.
This pic shows versions five and six. Turns out the fix has a problem. The audio current through the receive-side relay is more than it can handle. Radios that were used mobile would burn out the contacts in the receive relay and kill the receiver audio. Lasted longer in a base radio. Volume doesn't get turned as high.
Oops.
Can't get a relay rated for 3 Amps small enough to fit two of them. Decided to use a transistor to key the radio's transmit wire, and a single relay for the speaker.
At least it fits. Just one problem. Getting the layout right.
Not the end of the world. With trace cuts and a bodge wire it works as desired. Just can't sell a board with this kluge on it. Wouldn't be professional.
Besides, I installed the relay in half of them before discovering I had a trace underneath it that shouldn't even be there to begin with. It's the same trace that's on the solder side, just failed to see it.
Couldn't (wouldn't) very well remove those relays to cut this trace. Fixed the art errors, and ordered another batch.
So here is the revised board, going into a Philippines Cobra 148, first guinea pig for version 8. The 3-Amp relay had better dern well be big enough to last a while.
Yeah, the "P2" hole was empty in the previous pic. Pin 2 of the 5-pin socket connects to an axial RF choke with yellow sleeve on the leads. Wont'reach the board until it's bolted in place.
Works a treat, as the aussies would say. Yeah, version eight. Spared you the rest of the incremental learning experiences.
Maybe version eight is finally ready for prime time. But not before a few dozen of them get made.
Sounds easy.
73
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