Topics

HF9V with TBR-160S support needed


Steve K1ST
 

I have a 160-6 meter HF9V that exhibits high SWR when I apply more than 10 watts or so. My IC-7300 folds back on the output, then the SWR comes down and it tries to go back to full power and it keeps cycling up and down.

I've tried cleaning the connections for the door knob capacitors and cleaned the insulator in the middle of the mast. Sometimes it works for a little while and then starts up again. I've been running a lot of FT8 so the antenna is seeing a lot of 50-80 watt 15 second keydown sequences. The problem initially seemed to start on 80 meters but now affects all bands.

Any suggestions on what might be the culprit? I'm a bit stumped at the moment. I've owned four or five HF6Vs over the years but never seen this before.
73, Steve, K1ST


Tom Parkinson
 

Take a REAL close look at the capacitors. If you spot ANY hair line cracks - it's probably bad.  Freq will drift when the caps are hot from modes like FT8.  Possibly re-tune 80 to get the normal SWR as low as you can. SWR being up can heat up the caps as well.


On Fri, Aug 28, 2020 at 1:28 PM Steve K1ST <stolf73@...> wrote:
I have a 160-6 meter HF9V that exhibits high SWR when I apply more than 10 watts or so. My IC-7300 folds back on the output, then the SWR comes down and it tries to go back to full power and it keeps cycling up and down.

I've tried cleaning the connections for the door knob capacitors and cleaned the insulator in the middle of the mast. Sometimes it works for a little while and then starts up again. I've been running a lot of FT8 so the antenna is seeing a lot of 50-80 watt 15 second keydown sequences. The problem initially seemed to start on 80 meters but now affects all bands.

Any suggestions on what might be the culprit? I'm a bit stumped at the moment. I've owned four or five HF6Vs over the years but never seen this before.
73, Steve, K1ST


 

Why do people think that FT-8 produces unusual demands on equipment?  I am thinking that the duty cycle (15 seconds transmit then 15 seconds receive) is much less than other modes particularly a normal FM QSO. 

--
Al
WB9UVJ


Peter VA3PET
 

You've done the usual antenna checks but perhaps you have moisture in your coax?

Pete de va3pet va3hr


From: Butternut@groups.io <Butternut@groups.io> on behalf of Al WB9UVJ <markaren1@...>
Sent: Saturday, August 29, 2020 11:15:22 AM
To: Butternut@groups.io <Butternut@groups.io>
Subject: Re: [butternut] HF9V with TBR-160S support needed
 
Why do people think that FT-8 produces unusual demands on equipment?  I am thinking that the duty cycle (15 seconds transmit then 15 seconds receive) is much less than other modes particularly a normal FM QSO. 

--
Al
WB9UVJ


Fernando Martinez
 

Hi Steve,

just a question , the high SWR is in all bands or only in 160 mtrs ?. 

Fernando, EC3A. ( EA3KU since 1979 )


Eduardo PY1EB
 

Hello Steve.
I have a HF9V 160m to 6m also and I have the same problem. It started last week.
The problem occurs in 160m and slightly in 80m (the instructions manual of TBR-160-S kit says that the 160m adjustment can affect 80m and 40m).
If I use low power (<50W) the resonance point in 160m is kept fix. But if I increase the power the resonance point starts to change.
Exemplo: At the begning I have 1.1 SWR in 1850kHz. If I transmit two sequencies of FT8 using 200W the resonance goes to 1870kHz. After that I have to compress the 160m coil to fix the problem.
Well, now I have to work it.


Eduardo PY1EB
 

Hello Tom.
You are right!
One of two 200pF capacitors had hair line cracks (almost impossible to see, a very good cleaning helps). The bad capacitor has its capacitance varing from 200 to 1900pF.
Why did it happen? Time life? UV rays?
 
73.
Eduardo - PY1EB


Tom Parkinson
 

Many things can cause a crack. Temperature changes, mechanical stress, even slight stress at the wrong time. Some have cracked when tightened just a bit too much. They are just a bit fragile.

-------- Original message --------
From: "Eduardo PY1EB via groups.io" <py1eb@...>
Date: 8/31/20 14:36 (GMT-05:00)
To: Butternut@groups.io
Subject: Re: [butternut] HF9V with TBR-160S support needed

Hello Tom.
You are right!
One of two 200pF capacitors had hair line cracks (almost impossible to see, a very good cleaning helps). The bad capacitor has its capacitance varing from 200 to 1900pF.
Why did it happen? Time life? UV rays?
 
73.
Eduardo - PY1EB


 

Eduardo, the most common cause of cracking in certain climates is ice forming inside the cap and the resulting expansion causes the case to crack.
Al

--
Al
WB9UVJ


Steve K1ST
 

Thanks everyone for the suggestions. I found bad coax which now allows most bands to work. I think I have bad capacitors for 80 and 30 and have ordered replacements.

Thanks again. 73, Steve, K1ST