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Some more info and pictures for anyone wanting to use the uBitx on 160m.
I’m having a blast on 160m I did add larger heat sinks and a pair of small fans that I can turn on and off as needed to keep the finals cool if I’m long winded or using digital modes.
Qrp labs makes a great low pass filter kit:
On Feb 7, 2018, at 7:22 AM, bill richardson <ng1p.bill@...
160m doublet feed with 450 ohm line.
On Feb 6, 2018, at 9:23 PM, Vince Vielhaber <vev@...> wrote:
What are you using for an antenna?
On 02/06/2018 08:06 PM, bill richardson wrote:
Turned the output down to about 8 Watts and have made 4 contacts on 160 with great reports. Will add a larger heat sink to be safe.
On Feb 6, 2018, at 7:26 PM, bill richardson <ng1p.bill@...> wrote:
I don’t have a spectrum analyzer but I think your right. Without the LPF installed I’m seeing over 20 Watts out on 160m and with it I see 12watts out so a lot of signal outside of the 160m band is happening...
On Feb 6, 2018, at 7:12 PM, John Backo <jabac@...> wrote:
I think what you are seeing is the "normal" variation in the
output of the MOSFETS. Some are better than others at RF.
Gordon's suggestion to turn back the drive is probably the right answer.
Alternatively, you could turn down the gate voltage a bit, but that
would probably introduce compression distortion. Or you could increase
the size of the heat-sink and see how it goes. Probably the wisest thing
to do is both turn back the drive a bit and increase the heat-sink.
Some, but not all, IRF510's are capable of 20W or more on 80m.
you might happen to have some good ones. The key lies in the
harmonic generation and the heat-sinking.
Note that what you are seeing MAY be from UHF oscillation included in
the signal. Be very aware of that. Check your output very carefully.
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/