[Amps] 300Hz sidebands

[Conrad PA5Y]

Well of course initially I poured scorn on the complainers. But I have an E4406B spectrum analyser. So, I got a second opinion from myself. Sadly, they were right +/- 300Hz @ -50dBc. On VHF we can run a little more power before being castigated too much. I dislike FT8, not the mode but some of the users. There is no system in the world that can hear weak DX at the same time as a guy running 10W to a vertical who is 2 miles away. 

However, needs must. I don't like radiating a poor signal.

73

Conrad PA5Y



-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of Jim
Sent: 23 May 2021 20:03
To: amps at contesting.com
Subject: Re: [Amps] 300Hz sidebands

Reported by whom?
What did they use to measure it?
Did you get a second opinion?
Is it your exciter?
Are you over driving your radio from the computer?




Since you run 1KW on FT8, have you been put on the "BUD" list and banned from FT8 for life?


Everyone knows that you can't run more than 1 microwatt on FT8....



Thanks
73
Jim W7RY

On 5/23/2021 11:35 AM, Conrad PA5Y wrote:
> Hi all.
>
> I have several tetrode amplifiers that run from a 3PH 50Hz supply. With the advent of the FT8 I have become aware that I have 300Hz sidebands at only -50dBc, this is obviously unacceptable. The supplies are from Rhode and Schwartz and are very well made and use an 8uF oil filled capacitor for smoothing. Some of the EU amateurs will know the supply, it is known as an IN 026 A1.
>
> I suspect that this problem has always been there.
>
> What is interesting is that Class AB1 or Class C, 100W out or 1kW out from the PA the sidebands are -50dBc. I did consider the G1 and G2 supplies but 300Hz suggests the 3PH supply and this happens with 3 different amplifiers, the only common factor is the HT supply. If it was ripple, I would have expected this to change depending on Anode current, but it doesn't. Unless of course the capacitor is completely shot. I will check that next, it's a little difficult to get to.
>
> The PSU details can be found here:
> https://www.dropbox.com/s/l71qj1g3qv7zh73/Servive%20Doc%20UHN284.pdf?dl=0
>
> Any ideas?
>
> Regards
>
> Conrad
>
>
>
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