[NLRS] 70-cm Antenna Dilemma - Part II

[Dr. Gerald N. Johnson]

On Wed, 2006-06-07 at 23:44 -0500, Carl Estey wrote:
> 
> Many thanks to everyone who responded.  Here is the collective knowledge I
> gained from all of the responses and some answers to your comments.
> 
> The consensus is that that the unknown antenna is a KLM 440-16X.  That is
> correct - and I confirmed this from a 1995 AES catalog.  I do have a KLM
> 440-16X.  The specifications shown are:
> Bandwidth - 420-450 MHz
> Gain - 14.0 dBd
> F/B - Greater than 20 dB
> Balun - Coax "N" 4:1 2kW
> Beam - E = 28 deg; H = 32 deg.
> Boom Length - 10 ft 3 in

Don't expect that much gain. When it was made gain claims were wildly
exaggerated (Crumcraft still does), but it should have some gain. And
directivity and you should hear PQW better than at the noise. I suspect
balun and feed connection problems.
> 
> The 19th edition of the ARRL Antenna Book does have a large amount of info
> on various K1FO antennas however the 70-cm version is only 22 elements - and
> what I have is 25.  I still need data on the 25-element version.
> 
> There was a suggestion that I try a MFJ antenna analyzer to check the balun.
> That would be great but I don't have one.  I do have a MFJ that covers 160 -
> 144 MHz but doesn't make it to 432.  Anyone have anything I can borrow?
> 
> There was a suggestion that the connector in the radio might have a bad
> solder joint.  I would guess that to be unlikely since the radio is a Yaesu
> FT-897 and the same connector is used for 2-meters and 70-cm and 2-meters
> works well.  
> 
> Someone else asked if I am sure the is ok?  The problem is exhibited on both
> TX and RX.  The initial test was between Vince, K0VZJ and my station in
> Bloomington with results at noise level to a maximum of 4 S-units.  The
> second test was with Matt, KA0PQW tonight and the same results - noise level
> to S-2.  Also, I noticed that the solid state amplifier SWR warning light
> came on.  So the problem is mutual to TX and RX.
> 
> There were some other good questions asked - and here are my replies:
> Was it the same feedline ?  No - I had the problem with a 66' run of new
> LMR-400.  Then I tried a 48' run of Andrews 7/8" heliax.
> 
> Same jumpers in the shack ?  No.  A new LMR-400 ultra 15' jumper from the
> heliax to the radio.  Same results with a 15' jumper directly to the antenna
> at 8' above ground.
> 
> Same radio or transverter ?  No.  I did try my Microwave Modules 432-28
> transverter and had the same results with Vince, K0VZJ.
> 
> Same preamp ?  No external preamp.
> 
> How good are you measurements (i.e., 20 dB above the noise) ?  Probably not
> good at all as they are based on the Yaesu FT-897 S-Meter and my assumption
> that a S-unit equals about 6-dB.
> 
> How do you KNOW that you're down 40 to 50 dB ?  Who/what says ?  Like I
> said, somewhat guessing.
> 
> The K1FO antenna has not made it up the tower yet and the tests were solely
> in the backyard from a 8' mast with a 15' LMR-400 jumper to the FT-897.  The
> odd thing is that no amount of tuning the T-match got the SWR as shown on
> the internal FT-897 meter to get to 1:1.  The best I got was at 430 MHz.
> 
> Where/how did you measure the SWR ?  AT the antenna(s), or at the end of the
> feed line in the shack ?  Like I said, the measurements were with the
> radio's internal meter.  I do have a Bird 43 and slugs for 440 MHz so I will
> check it out.
> 
> Thanks to everyone who responded.  It has given me some things to think
> about.
> 
> 73
> Carl Estey WA0CQG
> wa0cqg at arrl.net
> (952) 250-3110 (Cellphone)

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer