backward swing

[Studebaker Hawk]

In an ideal design they'll do both.

The FL-7000 in my main shack is one example. There's a rear-panel switch which allows use with a high(er) or low(er) output transceiver, all the while maintaining proper load impedance and input linearity.

Of course, this costs money.

In an ideal design they'll do both.

The FL-7000 in my main shack is one example. There's a rear-panel switch which allows use with a high(er) or low(er) output transceiver, all the while maintaining proper load impedance and input linearity.

Of course, this costs money.

Yes I know.

The drive power for most CB amps is lower than full power CB radios.

I had a HealthKit amplifier with resistors with coils around them, on the inputs of each tube that increased the required maximum power from around 50 watts, up to about 100 watts.

If running tube final radio things aren't so critical, but with the solid state CB radios, as the load on the radio changes with modulation, the protection circuit will reduce the output of the radio.

The "special" length of jumper between them, is supposed to provide a certain current point between them, that makes those things less critical.

In the 1970's those little amps didn't have high / low switches and had a lot more parts inside them that complied with the original model designs from the transistor makers.

Later, in the early 1980's, having high / low switches was a selling point.

 

[Shadetree Mechanic]

There is a protection circuit on cb radios that reduces the output power if the SWR goes up?

 

[Studebaker Hawk]

There is a protection circuit on cb radios that reduces the output power if the SWR goes up?

There is a protection circuit on cb radios that reduces the output power if the SWR goes up?

Yes, there is.

 

[N8YX]

Yes, there is.

On most of the better ones. I've had to replace finals on a number of them which didn't incorporate it.

Same on a lot of the early solid state, 100w PA ham rigs. HW/SB-104 and TS-180S are two which readily come to mind.

 

[Studebaker Hawk]

On most of the better ones. I've had to replace finals on a number of them which didn't incorporate it.

Same on a lot of the early solid state, 100w PA ham rigs. HW/SB-104 and TS-180S are two which readily come to mind.

Yes, I've seen some burned out finals in CB radios too.

Even without power reducing protection, they are designed to produce their rated power into a 50 ohm load and will produce less power as the. SWR increases.

 

[bob85]

What protection circuit ?

solid state HF sets even most of the early ones like yaesu ft301d have couplers, sometimes called cm couplers or directional couplers on the output for vswr fold back protection,

CB radios are too basic to have any protection, no couplers reducing output when the load is mismatched,

CB's output whatever they can manage into the resistive or complex impedance terminating the antenna socket,

various things can cause a watt meter to swing backwards in AM mode,
none existent protection circuits in solid state cb's is not one of those things,

please give VA7JHI his book back

​

 

[N8YX]

Even without power reducing protection, they are designed to produce their rated power into a 50 ohm load and will produce less power as the. SWR increases.

Right up until the Pd figure is exceeded and they don't. Spec'ing a device with little or no headroom is a sure-fire way to see this happen in a PA strip which lacks active protection.

On the flip side: CPI incorporated power-limiting circuitry but also used devices which were rated very conservatively. As in, capable of several times the output at which they're run. Others (e.g., Stoner) derated their transmitters to safely utilize an MRF-476 at 2:1 VWSR without damage.