between radio and amp issue

[1iwilly]

I'm having an issue with SWR on my Palomar 300A between the radio and the amp. when in low power best i can get turning the trimmer on the low side of the switch or using a longer or shorter jumper is 1.8 SWR on high input and the output is 1.1 SWR. i got the same results using my ft-101e, my ft-890 or my cobra 148. i want to get it down because once i get my ham license back next month i want to use this amp on 10 and 40-meter i have 6ft from radio to amp and 6 ft from amp to bird meter. stupid question of the day do i have to retune the amp's front 2 tuners when using on low power ??? then redo the trimmer ?? my brain is overloaded from all the studying

 

[dave457]

Try a small ant. tuner between the amp and radio

 

[1iwilly]

OK i took a shot and re-tune the amp on low SWR Now 1.5 swr between the radio and amp switch over to bird meter reflects is 1 watt on a 25-watt slug
before re-tuning all i saw was 200 watts of output now pep 580 pep so it seems i made improvement but would like to bring them SWR a tad more down

 

[nomadradio]

Just remember that the band selector is a fraud, because it only has the one 10/11-meter input circuit each for high and low. Selecting 20 meters just won't work right. The input SWR would be stupid high.

Sometimes squeezing or stretching the associated coil slightly will improve the input match. Just don't overdo it and break the switch where the low-side input coil is mounted.

You found that the output tuning has a large influence on the amplifier's input SWR. Sometimes it's a back-and-forth between output and input tuning to find a sweet spot.

73

 

[1iwilly]

Just remember that the band selector is a fraud, because it only has the one 10/11-meter input circuit each for high and low. Selecting 20 meters just won't work right. The input SWR would be stupid high.

Sometimes squeezing or stretching the associated coil slightly will improve the input match. Just don't overdo it and break the switch where the low-side input coil is mounted.

You found that the output tuning has a large influence on the amplifier's input SWR. Sometimes it's a back-and-forth between output and input tuning to will happen with 40 meters ???

will that also be the same scenario with 40 meters ?? as you mention on 20

 

[nomadradio]

Yep.

73

 

[nomadradio]

The band selector was a fraud intended to get them around the FCC rules of the day. Take off the top and you can see resonant circuits for the driver's plate circuit and the final that are tuned for several ham bands. Makes it legit ham gear, right?

But they didn't spend the money to band switch the input circuits. They knew who was buying the 300A and why. It was a fig leaf that covered the private parts as seen from above. But not from below the chassis.

Separate input-matching circuits for each band would have added cost to the design. Wouldn't make it sell any better, so that "feature" was thrown overboard.

Not so much lipstick on a pig, more like a Nixon mask on a pig.

73

 

[1iwilly]

The band selector was a fraud intended to get them around the FCC rules of the day. Take off the top and you can see resonant circuits for the driver's plate circuit and the final that are tuned for several ham bands. Makes it legit ham gear, right?

But they didn't spend the money to band switch the input circuits. They knew who was buying the 300A and why. It was a fig leaf that covered the private parts as seen from above. But not from below the chassis.

Separate input-matching circuits for each band would have added cost to the design. Wouldn't make it sell any better, so that "feature" was thrown overboard.

Not so much lipstick on a pig, more like a Nixon mask on a pig.

73

so in layman's term not good for 20,40 meters with out spending money on matching networks

 

[nomadradio]

And the switching needed to make the input circuit's band match the band selected for the output side.

Doesn't appeal to me.

73

 

[Staybolt]

I'd sell it and look for a used Ameritron 811a amp or maybe a nice 3-500 amp if you go ham.