High swr between radio & amp

[Hulkster]

Good afternoon.
When I use my Boomer 250 to drive my Heathkit SB-200, I have no problems with SWR. But when I use my HF rig (Yaesu FT-ONE) to drive the Heathkit, the SWR between the radio and the amp is too high (2.5). What could be the problem?
Another way to say it >

- CB radio + Boomer + Heathkit > No problem.

- FT-ONE + Boomer + Heathkit > No problem. (Sometimes I use the FT-ONE to drive the Boomer (obviously with very low power).

- FT-ONE (alone) + Heathkit > here there is the problem. (High swr between radio and amp, but after the amp i put the meter and the reading is 1.1
What could be happen?

 

[W5LZ]

What SWR do you get if you line it up as;
FT-1 + SB-200, BUT with the SB-200 in stand-by, or, with the SB-200 off?
- 'Doc

 

[lords]

the SWR between the radio and the amp is too high (2.5). What could be the problem?

you need to run the meter after the amp...
why you running it in between the radio and amp?

 

[paws264]

That's a good question, you have come to the right place for the answer.

Let me re-state the problem to make sure that I have it right; When you use your Boomer (tube type amp with a load tune that adjusts the match into the final tube amp) into your big amp, you don't have any problems but, when you use you Solid-state output (with no external way to adjust the match to the antenna load AND it has a SWR protection circuit in it) radio to drive the final tube amp the Solid-State radio acts up.

The interesting thing is this, the Boomer has not input tuning but the FT-ONE is "OK" with it while, the Heathkit has built in input tuning that is not working as for as the Yaesu radio is concerned.

Pretty easy to figure out and fix; your Yaesu does not like the match that it sees going into the Heathkit. You can either,

1. Get a copy of the manual, look to see which of the input tuning slugs you need to adjust for the particular frequency that you are using.

2. Get an external Pi-Network tuner and put it between the Yaesu and the Heathkit and adjust you "match" so the the Solid-State radio sees a load that it can transfer 100% of it's power to.

Another conclusion that can be reached for what you are saying is this; Tube amps make better drivers for tube amps than transistor output devices.

BTW: For what ever reason, you were getting a bunch of "Hetrodyne" about where you ran your meter and what you were concerned over. Yes, it is a great idea to run watt meters between your radio and the amp as well as the amp and the antenna.

 

[Hulkster]

What SWR do you get if you line it up as;
FT-1 + SB-200, BUT with the SB-200 in stand-by, or, with the SB-200 off?
- 'Doc

1.1
swr is increased only when i activate the Heathkit’s relay

you need to run the meter after the amp...
why you running it in between the radio and amp?

For test purposes only.

That's a good question, you have come to the right place for the answer.

Thanks!

Let me re-state the problem to make sure that I have it right; When you use your Boomer (tube type amp with a load tune that adjusts the match into the final tube amp) into your big amp, you don't have any problems but, when you use you Solid-state output (with no external way to adjust the match to the antenna load AND it has a SWR protection circuit in it) radio to drive the final tube amp the Solid-State radio acts up.

No. The Boomer is a small solid state amplifier, with two 2SC2290’s transistors (same transistors of FT-ONE) :shock:
For that reason the problem is more difficult (or strange) that they appear.

your Yaesu does not like the match that it sees going into the Heathkit.

Apparently no.

Get an external Pi-Network tuner and put it between the Yaesu and the Heathkit and adjust you "match" so the the Solid-State radio sees a load that it can transfer 100% of it's power to.

Is one of the possibilities that I have analyzed, but I’m still with the doubt. Both equipment has the same final transistors (HF rig and Boomer). Why when i use Yaesu + Boomer + Heathkit, all work’s fine, but when i use Yaesu + Heathkit, the problems come.

Today i’m gonna make more tests, in different bands.
i´m going to put my other rig (FT-101B) in place of the FT-ONE to see if happens the same.
Thanks for your answers.

 

[W5LZ]

As some one said before, just depends on where that SWR meter is placed. If it's right after the FT-1 and before the solidstate amplifier, then the meter (and FT-1) only see the match between the FT-1 and solidstate amplifier. If the meter is between the solidstate and the SB-200 then it sees any mismatch there. If it's a good match then low SWR, and can mean that the output of the solidstate and SB-200 are the same (not necessarily right, just the same, or the output circuitry of the solidstate amplifier can 'compensate').
The 'cure' sounds like the input of the SB-200 isn't what it should be, and probably needs adjusting. That's why ALWAYS having the manual is very nice.
- 'Doc

Oh, the FT-101 probably won't object near as much as the FT-1. Probably the same mismatch, the FT-101 is just more tolerant because of the way it's constructed. The solution is still the same, fix the SB-200.

 

[Hulkster]

Well, here is the test results:

With the FT-101B happened the same, in 10, 11 and 15 meters band (in this moment i don´t have 20 meters antenna). But in 40 meters, both radios work fine with the SB-200, without SWR problems. So, for that reason I assume that the problem is in the SB-200. Unfortunately, in this moment i don’t have the Boomer with me to repeat the test in 10 - 11 meters band.
What could be the problem with the Heathkit?
Thanks for your answers.

 

[W5LZ]

There could be several things not right with that SB-200. Remember that all except a very few of them were built by people who may not have been the best builders in the world. The number of SB-200s ever adjusted by HeathKit could probably be counted on the fingers of one hand. So, taking a look on the insides of the thing is a fairly good idea. So is having that manual for it!
Depending on who built the thing, they may not have bothered with the 10 meter circuitry. Or maybe 'adjusted' it for another band, who knows. I seriously doubt if that 10 meter input circuit is going to cover both 10 and 11 meters. Individually, yes. Both together, I doubt it.
Smartest thing you could do is beg/borrow/buy a manual, both operating and building, for that SB-200. Good luck.
- 'Doc

And just out of curiosity, why a solidstate amplifier for a driver? Not all that familiar with a FT-1, but I seriously doubt if it needs the 'help'.

 

[Hulkster]

Smartest thing you could do is beg/borrow/buy a manual, both operating and building, for that SB-200. Good luck.
- 'Doc

Yes, i have the building manual with the schematics and the parts list.
Well, it’s time to begin to work with the Heathkit.

And just out of curiosity, why a solidstate amplifier for a driver? Not all that familiar with a FT-1, but I seriously doubt if it needs the 'help'.

You’re right. The Boomer amplifier and the FT-ONE have the same final transistors (2 x 2SC2290). For that reason, both have more or less the same power. But... I take care very much the rig, and i avoid to use it at full power, so i prefer to use the Boomer when i need 100 + watts to drive the Heathkit at full power.
Thanks for your help!

 

[KC2OST]

you need to run the meter after the amp...
why you running it in between the radio and amp?

No he doesnt if he is checking the input swr of the Heathkit.

 

[hotrod]

im not familar with the ft radio ya using but why areusing 2
drivers for the sb200?im sure the radio will do the job
fine without stressing the radio out?

 

[KC2OST]

Good afternoon.
When I use my Boomer 250 to drive my Heathkit SB-200, I have no problems with SWR. But when I use my HF rig (Yaesu FT-ONE) to drive the Heathkit, the SWR between the radio and the amp is too high (2.5). What could be the problem?
Another way to say it >

- CB radio + Boomer + Heathkit > No problem.

- FT-ONE + Boomer + Heathkit > No problem. (Sometimes I use the FT-ONE to drive the Boomer (obviously with very low power).

- FT-ONE (alone) + Heathkit > here there is the problem. (High swr between radio and amp, but after the amp i put the meter and the reading is 1.1
What could be happen?

What type of meter are you using and are you modulating while checking the input swr of the amp. If so what does it do under modulation?