[amsat-bb] Re: Yagi Antenna Comparison
stargatesg1 at verizon.net
Thu Jul 5 17:04:18 PDT 2007
Thanks for the tips. I just ordered both the M2, 2MCP22 and 436CP42UG
and figured they will be a bear to construct.
Tips are always helpful when traveling uncharted waters:-)
A good friend will come and bail you out of jail,
A TRUE friend will be sitting next to you saying.....
"DAMN THAT WAS FUN"
> -----Original Message-----
> From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org]On
> Behalf Of Alan P. Biddle
> Sent: Thursday, July 05, 2007 4:47 PM
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] Re: Yagi Antenna Comparison
> I recently replaced some 20 year old KLMs with M2s. In most ways, the M2
> are BMWs and the KLMs are Yugos, though they did a good job. (I
> need to do
> a little refurbishing on the KLMs, and will probably have them
> for sale if I
> am satisfied with them.) If you get the longer versions of each M2,
> recommended, be prepared for poorly written documentation with
> some cut and
> past from the shorter versions which is simply wrong in one case, and very
> confusing in others. You can sort it out by phone easily enough, since M2
> does not return e-mail or phone messages in my experience. Still, for
> drawings dated 2000 to be this seriously in error, and not
> updated, does not
> speak well for them.
> There were also a few parts, sealing rings for the type F
> connectors, which
> were missing. However, because I also ordered the CP switches, which had
> extras, I had enough. Finally, on the 70 cm unit, there are some
> very tight
> bends at the connectors for the phasing and switching lines. These need
> very gentle installation, and some additional water proofing.
> There is more
> than enough length on the 2 meter version. I didn't take the same to work
> it all out, but if they had added a wavelength to a couple of lines, or
> perhaps .5 wavelength to several, the needed phasing would have been
> preserved, and there would be no strain on the connectors.
> I checked everything I could think of on the ground, and found
> the SWR, and
> the change with polarization, much better than with the KLMs. When I got
> the 2 meter version up, purely as an accident because of the
> particular SWR
> meter I use, I found that there was a 1K ohm or so short between
> the rf and
> dc switching lines in the 2 meter unit. I ended up opening the switching
> unit, easy enough, and found two things. First, the dc lead to the
> switching relay was just barely touching one of the rf leads. It was easy
> to move the dc lead away, but the problem was highly visible, and should
> never have been sold that way. Second, there were a couple of
> places where
> the rf wiring was connected using solder bridges because the wires were
> poorly installed. Again, easily fixed, and totally unacceptable
> for a unit
> which lists for $201.
> The overall impression is an outstanding design, with great attention to
> detail, spoiled by some mind boggling carelessness in execution of rather
> small but important things.
> Once you get them up and debugged, they really work well. The KLMs had
> significant side lobes, and it is obvious that the M2s are quite a bit
> better from that standpoint, though I can't do AB measurements. While I
> never had any problems getting into AO-7, FO-29 or VO-52 with the KLMs, I
> have noticed that I need to back off on the TX power
> significantly more than
> before to have a socially acceptable signal strength. The same
> on AO-51 and
> the other FM birds. Of course, it is nice to be able to crank up
> the power
> when shooting through the trees, or when the bandits are on the AO-51
> uplink. Now all I need to really test them are some P3 birds.
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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