Hi Dick,
I normally run barefoot to a coax fed OCF dipole at 40ft, a compromise antenna.
I print others but it seems no one can hear me. A few months ago a good friend
gave me a broken AL-811 with 6 spare "Jetstream" 811a. Issue turned out to be a
shorted metering diode (1N4007). The original Svetlana 811a were soft (50w
exciter gave 100w on amp) so I swapped the "Jetstream" in. While they lasted
(almost 2 weeks) - which I presume their going soft was attributed to a leaky
Plate caps, or just poor quality Chinese tubes. I used tube amps in the army in
our Rat rigs, so amp tuning is a quick thing here.
To your point, I decided to try this on a Thursday NS RTTY session. I found
that 10w exciter could easily drive the AL-811 to 100w. 20w would net 200w. The
difference a 200w was pretty amazing here. The max I drove it to was 250w as
that is the limit of my dipole. I soon went back to barefoot as there was a
small, but noticeable delay between TX and RX switching that I was not happy
with that truncated printing, though some deliberate timing efforts could and
most likely would improve that. I did not notice any unusual heating or other
detrimental issues at these power levels. This was also powered off the typical
branch 110v outlet.
Running the 572b tube would provide added buffer over the 811a since they are a
significantly more robust tube and share the same 4 pin socket. You wont get
any more power, just peace of mind and longer tube life should you accidentally
have a case of the "stupids". With 572b, I do not see any issues running RTTY
400w out in the AL-811. Should you stay with 811a tube, I would not go over
300w RTTY. I believe this is Ameritron's advice for this amp and mode; if there
is a smart guy out there that can opine, please chime in.
As for the interface, I did not use one here and my rig is IC7410. If you want
complete assurance that your rig will be protected, by all means, get
Ameritron's ARB-704 keying buffer or something like the "Key-All" from Jackson
Harbor Press. The Key-All will give some building fun! This all depends on how
robust the keying circuit is in your rig and what the requirements are of the
amp. I think the ARB-704 is largely unnecessary for many out there, BUT, there
are a lot of ops that don't or won't read what these specs are and simply
connect everything and see if it works.
I am more of a CW op and I cannot stand sending blind as there is no QSK in the
AL-811. This is not an issue for RTTY or SSB operating, though the previously
mentioned TX-RX switching delay may not be acceptable for you. I was looking
for an amp with QSK but my wife surprised me and picked up a Ten Tec 411 with
572b (Ten Tec's 600w amp with built in QSK). For all but the most demanding op,
my opinion is the first 400w does all the work and I cannot see a point where I
would need anything more than that for the operating I do here.
Hope this helps.
73
Mike N4EEV
ex WH6YH
> On May 26, 2017, at 10:41 AM, rtty-request@xxxxxxxxxxxxxx wrote:
>
> I am working RTTY about 90% of the time now as I can't copy CW as I once
> did. With propagation as bad as it is I am considering buying an amp. Have
> not had one for over 15 years. On RTTY I can copy many calls but they can't
> copy my 75 watt signal on my 4 element beam and that is frustrating.
>
> With a limited budget I am considering a AL-811H or the AL-811. I would
> like to know how either rig works with RTTY. Also how much output power
> from the rig do they need to get 200 or 300 watts from the amp. Also, the
> Ameritron video on the 811H shows using an interface to protect the radio.
> Is this really necessary?
>
>
>
> Replies appreciated.... Dick KS0M
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