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swr goes up when amp is used

airplane1

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
Anyone know why and if it is normal for the swr to go up when amp is on and in use? I have an ameritron al-811 and the swr on the radio is 1.2 to 1 when talking on radio alone, when I switch on the amp and talk the swr swings up to 2.0-3.0 to 1.

I dont know if the radio is just seeing this from the amp being turned on or what. I know my swr of the antenna is 1.2 on my mfj 259 and radio shows same till like I said the amp on changes it.

Help.

AP
 

yea, this is a comon problem, mesure your swr behind your amp. and adjust ther so the amp sees 50 ohms or flat swr. your swr between your radio and the amp, most of the time is oke.
hope this is of any help
Johan, EA5HIY
 
Hi EA5HIY,

Ok, this is what I am getting. I check the swr comming in to amp, this is my antenna coax and it is 1.2 to 1, very good. I check the coax comming out of amp and it is about the same 1.3 to 1. so it is all good. radio sees the same when only radio is on. now when amp is on it jumps to 2.5-3 to 1 in peaks to my voice. this is on my IC-7000 swr meter while talking.

So I cant adjust my antenna or anything as it is good now??
 
airplane, most of the tubetype linears are not flat 1:1 on the input side, so your driver rig sees something else as 1:1 this can be corrected, BUT you have to make adjustments in the AMP, not in your rig. to do this, you have to be familiar with the amp and the guts of it !!be carefull with the HV inside !! better if your not in to this, have it done by a HF specialist, friend or fo.
are you using it on 11 or in the ham bands ?
cause the amp maybe ok in the HAM bands but not on 11
Johan
 
oke, you should look in " Circuit Improvements for the Heath SB-220 Amplifier.
there is an article writen by Rich, AG6K everything about the SB220 .
I think you can find all the answers there, if not, there is a group in YAHOO users with a forum, BUT you must have a legal hamcall cause they willnot help you if the think you will use the amp on 11.
personaly I dont mind, cause its your own responsebility, not mine but with the Ham spirit in mind I help every one I can.
73,s de EA5HIY Johan
 
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thank you, I will def look on the yahoo group. I belong to the IC-7000 yahoo group. I am a ham so I am legal. I still talk on 11 but it is with a legal radio.

thanks again, I will look where you said for info.
 
I ran into a "higher power-higher swr" problem when I was trying to figure out what I was doing wrong with my 5/8 wave. It turned out to be an induction problem, but the symptoms were the same. The more I turned up the power the worse the swr got.
Not at all saying it's not the previously mention issues just throwing out a thought.

Have you used power with that antenna before?
 
airplane1 said:
Anyone know why and if it is normal for the swr to go up when amp is on and in use? I have an ameritron al-811 and the swr on the radio is 1.2 to 1 when talking on radio alone, when I switch on the amp and talk the swr swings up to 2.0-3.0 to 1.

I dont know if the radio is just seeing this from the amp being turned on or what. I know my swr of the antenna is 1.2 on my mfj 259 and radio shows same till like I said the amp on changes it.

Help.

AP
Click to expand...

Find yourself a Workman PDC 5 SWR Meter and Matcher, put it in between your radio and the amplifier and use it to adjust the "SWR" (input tuning) into the amp. Turn the Matcher off when not using the amp.

.
 
EA5HIY said:
dear Slamdunk, thats not the way to do it Hi Hi.
73, sde EA5HIY Johan
Click to expand...

I agree, do not put any kind of tuner between the radio and the amplifier, that is a band-aide that is not needed and a waste. The Ameritron 811 series has a tunable input, those are the inductors you see from the back of the amplifier for each band section. You need to obtain a plastic tuning tool, call Ameritron, they can probably supply you with the tuning tool and tell you how to set up the input on the amplifier. Not sure if you bought it used, but sometimes folks will tinker with the input to get the SWR down on their particular slightly out of resonant antenna system or in shipping they can get jolted out of tune.

Nevertheless, if you have a big enough dummy load, I suggest that you set all the bands up into a load, not an antenna system. Always best to work with a known load so all impedances are equal.

Good Luck,

73
 
295 said:
I agree, do not put any kind of tuner between the radio and the amplifier, that is a band-aide that is not needed and a waste. The Ameritron 811 series has a tunable input, those are the inductors you see from the back of the amplifier for each band section. You need to obtain a plastic tuning tool, call Ameritron, they can probably supply you with the tuning tool and tell you how to set up the input on the amplifier. Not sure if you bought it used, but sometimes folks will tinker with the input to get the SWR down on their particular slightly out of resonant antenna system or in shipping they can get jolted out of tune.

Nevertheless, if you have a big enough dummy load, I suggest that you set all the bands up into a load, not an antenna system. Always best to work with a known load so all impedances are equal.

Good Luck,

73
Click to expand...


That's the correct way to do it. There should be a tuning slug for 10-12 meters. If you talk on both 10 & 12 meters, you're going to have to adjust it somewhere inbetween that makes the radio fairly happy. You can also sometimes find one of the plastic TV repair tool kits that will have one with the correct size...it's an alan size (metric, if I remember correctly). You can also do it with a regular metal wrench BUT you have to make a small adjustment, then TAKE THE WRENCH OUT before you key the transmitter to check it. Be careful.

I had to adjust the input tuning on several bands on my Ameritron AL-800H to make the rig happy...this is normal.
 
That's a 0.1" hex plastic tuning tool you need. Follow the procedure in the Ameritron manual.

SWR does NOT increase with power unless something is drastically wrong with the load or the feedline.
 

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