|[AMRadio] Legal-Limit tuner advice....?|
w1eof at hamnutz.com
Fri Aug 18 01:09:44 EDT 2006
Keep in mind that while the "T" tuners can match a wider range they also can
be mis-tuned into a mode where a lot of power is consumed in the coil yet
all looks good. This can't happen in a PI network for instance. It's a good
reason to have one or more RF ammeters around for monitoring your antenna
I prefer a link-coupled tuner like the MB for balanced loads, a parallel
type tuner for end-fed wires and such, and a PI for coax-fed antennas. I can
tune my Zepp from 80-10 including WARC bands with the MB. For 160 I can feed
it as a "T" through a special link-matcher. You'll find many different
opinions except that I think everyone agrees the MFJ tuners are very cheaply
made. I have a 949 that I don't use that much... it's got flimsy components
in it. Fine for say 100W I guess but no more. The switches feel flimsy too
when you rotate them. I wouldn't recommend one that's for sure.
> -----Original Message-----
> From: John Lawson [mailto:jpl15 at panix.com]
> Sent: Friday, August 18, 2006 12:52 AM
> To: W7QHO at aol.com
> Cc: amradio at mailman.qth.net
> Subject: Re: [AMRadio] Legal-Limit tuner advice....?
> On Fri, 18 Aug 2006, W7QHO at aol.com wrote:
> > In a message dated 1/12/06 8:31:16 AM, jpl15 at panix.com writes:
> >> On Wed, 11 Jan 2006, W7QHO at aol.com wrote:
> >>> Quick and dirty, just try grounding one side of your
> ladder-line at the
> >> input
> >>> end and feeding the other side off the single ended output of
> your ATU and
> >>> see what happens. SWR figures might be better (but could
> also be worse).
> > John,
> > Did you ever try this? If so, what were the results?
> Yes, I did - results not good at all, antenna would not tune and the
> Transmitter complained at me bitterly... ;} I also built in a DPDT
> knife switch in the feedline after the tuner - it's mainly for grounding
> during t-storms, but I played around with various
> (semi-calculated) values
> of capacitors and coils... on 10 meters the use of various paralelled
> caps made improvements, but tuning became very critical, and there's
> nothing much that interests me up there - I *do* like to work 20M RTTY ,
> and have yet to try PSK32 into the Valiant.
> I'm still gathering facts, and the Listmembers have been quite
> helpful -
> everyone likes the Palstars, but the big Ten-Tec also has impressive
> specs.... I intend on converting a broadcast transmitter for use in the
> shack, so the Tuner needs to be able to withstand 100% duty-cycle at
> Legal Limit. Ultimately I'll tune the feedpoint of the antenna itself,
> and just run 50-ohm line from the transmitter out to the
> "doghouse" if you
> John KB6SCO
> Who just shut the rigs off after a nice AM QSO on 80....
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