• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Texas Star DX-500V SWR issues on full output

skiman1

Member
Aug 28, 2014
57
25
18
33
When using my Texas Star DX-500V wide open, just power on, (no SSB delay or AM/Dial A Watt engaged) radio set to 2.5, dkey so amp output is 100w dkey and swings up, the SWR between the radio and Amp runs a little high via the SWR meter in the radio (stryker 955hp) from 1.7-2.0, but the SWR after the amp is fine, about 1.3-1.5 or so.

Alternatively when I run the amp with the AM/Dial A Watt engaged, SWR between radio and amp is near flat with the radio putting out a 50w deadkey and swings up. Now the funny thing here is if I increase the radio dkey to 4.5 to get 100w dkey out of the amp with the AM/Dial A Watt engaged, the SWR is STILL near flat between the radio and amp!

Next question, is it OK to run the amp with a 4.5w deadkey with the AM/Dial A Watt engaged to get 100w dkey instead of having the AM/Dial A Watt NOT engaged and having these higher SWR's? I know that the AM/Dial A Watt circuit acts as a input pad vs controlling the output so it SHOULD be good to do that, right or wrong?

I've tried swapping out cables of different lengths and got that radio to amp SWR a little lower, it was around a 2.0 across the band and with some different combo of cables has come down some, but never flat with like with the AM/Dial A Watt engaged. Again, AFTER the amp, never an issue, 1.3-1.5 or so.

Thanks for any help!
Skiman1
 

If the radio has been hacked with mods, then it may well be throwing out harmonic freqs. If the harmonics are strong enough; then it will alter the SWR from the radio. To test this , you will need to use another radio that hasn't been messed with - and then re-test.
 
Last edited:
  • Like
Reactions: wavrider and RT431
Thanks for the reply's guys, sorry, didn't even realize anyone replied, the site was down right after I posted this and I never got notifications of replies. I will go over what everyone said when I get home later, thanks again!
 
Would love to hear how you make out, skiman.

Thinking about your question with respect to the “am” button - I believe most people run into issues when their radio is too powerful and they try to compensate with the dial a watt knob. If you’re able to achieve desired results with the am button in, 4.5w deadkey, and dial a watt fully clockwise, I would be hard pressed to imagine you’d have problems.

There’s some folks here that have seen the inside of these amps a million times, and have direct experience with dial-a-watt failures.

I’d be very curious to see what they have to say about running it that way, with 4.5 watts in.
 
  • Like
Reactions: skiman1
I personally do not ever use the Dial-a-Watt knob feature .... just never have ....
On a few Texas Star DX 500V amplifiers, I have completely bypassed the adjustment knob.
I do prefer to control with the variable power on the radio instead.
 
  • Like
Reactions: S&W357 and 2NC995
You are correct in that the SWR becomes flat due to the resistive input pad. This doesn't actually fix the problem of power being reflected from the input though, and the pad/attenuator is just absorbing the reflected power, in the same way it absorbs some of the input power, so it's not making it all the way back to the radio. Changing the length of the coax doesn't have any effect on the amount of reflected power either, but it does change the phase so it can cause false/misleading readings from a radio's SWR bridge. The best fix is to adjust the actual input circuit of the amp. You should be able to get it flat across all 40 channels.
I'm with Ranch, I never use the variable on an amplifier either, and I've also completely removed the knob from a few 400V & 500V amps in the past. Output power is better controlled by varying the power at the radio in my opinion. Also, as others have mentioned, out of band emissions from the radio can cause a higher than normal SWR between the radio and the amp. These emissions are quite common with the 955/655/447HPC2/AT6666 radios and get worse when the power is turned way down.

73s and good luck.
 
  • Like
Reactions: skiman1

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Tucker442 has left the room.
  • @ BJ radionut:
    LIVE 10:00 AM EST :cool:
  • @ Charles Edwards:
    I'm looking for factory settings 1 through 59 for a AT 5555 n2 or AT500 M2 I only wrote down half the values feel like a idiot I need help will be appreciated