Topics

uBitx V5 and JS8Call - Losing tx power on long transmissions. #ubitx #v5 #js8call

Jimmy Capizzi
 

Hello.

I am working portable with a uBitx, and a Linux laptop for the first time today, everything seemed fine, but my first qso, when sending my info, 3 min transmission, I was watching the meter and the power dropped down to almost nothing 3/4 though the tx. My receiving station, KB9HP, was unable to decode the entire message.

Any idea what's going on? Are my finals going bad already? 

Any feedback would be really appreciated.

Jimmy
K3CHB

Jakobus van der Merwe
 

On the face of what you said, I would say, keep a eye on the supply power if you transmit. if it stays constant or drop slightly, then your power supply is fine. If it drops slowly and quite a lot. Then your power supply is not up to its task. A supply that output higher amps should be used. If the power supply is ok. Then it is the final transistors getting hot. The efficiency will drop. Remedy here will be to use bigger heatsinks on them and even use a fan to cool things down. This is a classical simptome of overloading on a power supply or no sufficient heatsinking on the transistors. Do not carry on till you fixed the problem. Because either the power supply or transistors will go on retirement eventually.

J van der Merwe

On Sun, 28 Jul 2019, 08:42 Jimmy Capizzi <thechubb16@...> wrote:
Hello.

I am working portable with a uBitx, and a Linux laptop for the first time today, everything seemed fine, but my first qso, when sending my info, 3 min transmission, I was watching the meter and the power dropped down to almost nothing 3/4 though the tx. My receiving station, KB9HP, was unable to decode the entire message.

Any idea what's going on? Are my finals going bad already? 

Any feedback would be really appreciated.

Jimmy
K3CHB

 

Jimmy,

Your finals are getting too hot. Put them on a bigger heat sink.

You should notice that after it cools down the power will be back.

Raj

At 28-07-19, you wrote:
Hello.

I am working portable with a uBitx, and a Linux laptop for the first time today, everything seemed fine, but my first qso, when sending my info, 3 min transmission, I was watching the meter and the power dropped down to almost nothing 3/4 though the tx. My receiving station, KB9HP, was unable to decode the entire message.

Any idea what's going on? Are my finals going bad already?

Any feedback would be really appreciated.

Jimmy
K3CHB

Gordon Gibby
 

​Perhaps you're overheating those finals or clobbering your battery.... you might feel the heatsinks, and reduce the power a tad.   3 minutes is a lOOOOOOnG time to transmit.      


if the trnsmitter works fine at the start of the NEXT transmission....no harm done.

Gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of Jimmy Capizzi <thechubb16@...>
Sent: Sunday, July 28, 2019 2:42 AM
To: BITX20@groups.io
Subject: [BITX20] uBitx V5 and JS8Call - Losing tx power on long transmissions. #ubitx #js8call #v5
 
Hello.

I am working portable with a uBitx, and a Linux laptop for the first time today, everything seemed fine, but my first qso, when sending my info, 3 min transmission, I was watching the meter and the power dropped down to almost nothing 3/4 though the tx. My receiving station, KB9HP, was unable to decode the entire message.

Any idea what's going on? Are my finals going bad already? 

Any feedback would be really appreciated.

Jimmy
K3CHB

MVS Sarma
 

I replaced the heat sinks with a single strip heat sink with suitable insulating kits. Now they run cool.
it is 1.25" height , 4" long and 0.3" thick.
You  may also try.

regards
sarma
 vu3zmv


On Sun, Jul 28, 2019 at 5:36 PM Gordon Gibby <ggibby@...> wrote:

​Perhaps you're overheating those finals or clobbering your battery.... you might feel the heatsinks, and reduce the power a tad.   3 minutes is a lOOOOOOnG time to transmit.      


if the trnsmitter works fine at the start of the NEXT transmission....no harm done.

Gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of Jimmy Capizzi <thechubb16@...>
Sent: Sunday, July 28, 2019 2:42 AM
To: BITX20@groups.io
Subject: [BITX20] uBitx V5 and JS8Call - Losing tx power on long transmissions. #ubitx #js8call #v5
 
Hello.

I am working portable with a uBitx, and a Linux laptop for the first time today, everything seemed fine, but my first qso, when sending my info, 3 min transmission, I was watching the meter and the power dropped down to almost nothing 3/4 though the tx. My receiving station, KB9HP, was unable to decode the entire message.

Any idea what's going on? Are my finals going bad already? 

Any feedback would be really appreciated.

Jimmy
K3CHB

_Dave_ K0MBT
 

Agreed on the heat. Our uBITX radios will overheat finals with any prolonged transmission. Hi SWR will be bad as well. On the uBITX radios that we run in digital mode we have larger heat sinks and fans. I have used chunks of old computer heatsinks. On one radio, I isolated the screws and tied a piece of aluminum angle iron heat sink to the aluminum chassis and output finals. Works great no fan and no heat. I usually use an old standard uBITX output heatsink as a 7805 heatsink on the raduino board.

Dennis Beverage
 

It would be helpful/informative if some of you would include photo/s and source info re these custom heat sinks.  Seems like most of us should be using bigger heat sinks just as a matter of precaution.  Also, installing and isolating custom heat sinks could be tricky.  Thanks for your ideas though.
--
Sodypop🤠
KJ6VGB

Doug W
 

don't discount the heat removing power of a little moving air...
https://groups.io/g/BITX20/message/53168  
--
www.bitxmap.com

Dennis Beverage
 

Great tip Doug.  Looks like it would fit with most cases.  Probably would eliminate the need for bigger heat sinks in most cases.  I don’t even have a case yet, but I’m ordering one anyway.
--
Sodypop🤠
KJ6VGB

Jimmy Capizzi
 

Thanks for all the input guys, I got it worked out, and yes the finals were getting HOT!

What I ended up doing is putting a small fan on the back of the case, and I also turned down the power output (RV1 I think),cause I had it pegged full tilt.

On the js8 computer, I lowered the sound card output also, so it read the same as a CW carrier on the meter. Now I am working JS8Call on the uBitx successfully.

K3CHB

On Mon, Jul 29, 2019, 11:49 AM Dennis Beverage <Sodypop@...> wrote:
Great tip Doug.  Looks like it would fit with most cases.  Probably would eliminate the need for bigger heat sinks in most cases.  I don’t even have a case yet, but I’m ordering one anyway.
--
Sodypop🤠
KJ6VGB