[Lowfer] 1 watt in class " AB " into 32 Ohm load, BW - 600 KHz, and it's an audio amp

[jrusgrove at comcast.net]

Andy

PSK, BPSK, QPSK, WOLF generally require a linear amplifier although at least several lowfer stations 
have run some of those modes through non linear amplifiers with no problems. There's little chance 
that a PW 1-watt lowfer is going to cause intereference - especially if run outside of the watering 
hole window as is customary when transmitting a 'digital' mode.

RTTY, Pactor, Jason, Amtor, MFSK, Olivia, Domino, Throb, WSJT, WSPR do not require a linear 
amplifier and can be run through your existing lowfer 'Class D' final with no concerns.

Jay


----- Original Message ----- 
From: "Andy - KU4XR" <ku4xr at yahoo.com>
To: " European & UK) and MedFer bandsDiscussion of the Lowfer (US" <lowfer at mailman.qth.net>
Sent: Thursday, November 25, 2010 5:20 PM
Subject: Re: [Lowfer] 1 watt in class &quot; AB &quot;into 32 Ohm load, BW - 600 KHz, and it's an 
audio amp


> --- On Thu, 11/25/10, JD <listread at oswegoblade.com> wrote:
>
>>
>> We also need to bear in mind that Andy was asking about
>> Part 15 operation, which is limited to 1 watt DC INPUT.
>> The efficiency of Classes A and AB are pretty poor,
>> and B is barely adequate.
>>_________________________________________________________________
>
>
> Hi JD:
>
> I suppose that this fact is probably one of the biggest reasons
> that there are not many lowFERs sending linear modes on 1750 meters.
> 70% efficiency would be excellent performance in a Class " AB " amp.
> Unless I'm mistaken, I think the distortion in a Class " B " amp
> might be a little too high, but on the other hand; at LF would it
> even be noticable ?? Possibly so if it distorted the transmitted
> waveform of a digital mode enough that decoding it would be difficult,
> or impossible. I don't have enough experience to know.
> I did build an HF to LF Transverter using a SA612, and a TDA7052B.
> The IF was at 28 MHz, and I was trying to use an old Radio Shack HTX-100
> 10 meter mobile as the tunable IF. It works, but the drift in the old
> radio is excessive, so not very useful. Antenna current readings with
> the QRSS Class " D " setup on the old antenna were 180 Milliamps, and
> on the Linear Transverter set for 1 watt DC Input on the TDA7052B audio
> amp, the Antenna current was 110 Milliamps. So there is certainly a
> drop in output efficiency with any Linear system.
> I do still have the desire to get a Linear PA going at some time, and
> run something in addition to the QRSS signals on the band. Probably
> just need to change the crystal in the transverter, and use another
> radio as the tunable IF. I guess that's the most logical route to take.
>
> 73:
>
>
> Andy - KU4XR - EM75xr - Friendsville, TN. USA
>
>
>
>
>
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