[Heathkit] SA-2550 Antenna Matcher

[Robert & Linda McGraw (K4TAX)]

Mike brings up a good point here.  With the new frequency allocations for 
SSB and other modes, specially on 75 meters and 40 meters to some extent, 
antennas of additional bandwidth will certainly be desirable.  In general I 
am a firm believer that a center fed wire with a balanced feed and a good 
tuner will work wonders.  At the same time, for those that do not have or do 
not want to use an external tuner, I have found that the old fashion folded 
dipole constructed of 300 or 450 ohm line and fed with the same has a 
wonderful broad bandwidth.  Simply use a good 4:1 balun at the shack end of 
the feedline and that to the radio with it's internal tuner.

My most recent project was a 75 M folded dipole constructed from 300 ohm 
window line acquired from The Wireman and it has worked great.  I also find 
that it is quieter than the single wire dipole fed with coax, and is much 
broader in terms of SWR than the dipole.  It is cut for 3.800 and easily 
works +/- 200 KHz.  I made my end insulators/supports from some 1/2" 
Plexiglas blocks and the center feedline support also from 1/2" Plexiglas. 
Sandwich the line between the pieces so as not to place the support stress 
on the conductors and use stainless hardware to hold the blocks together.

73
Bob, K4TAX


----- Original Message ----- 
From: "Mike McCarthy W1NR" <mike at w1nr.net>
To: <heathkit at mailman.qth.net>
Sent: Friday, November 24, 2006 7:23 AM
Subject: RE: [Heathkit] SA-2550 Antenna Matcher


> It is the "Antenna Matcher" SA-2550.  I have two in service (160 and 80) 
> and
> one unbuilt (sorry, I'm not willing to let any of them go).  Bought the 
> last
> two when the local Heathkit store was closing down.
>
> It is a very simple design.  The capacitor is 8 1/2 inches long, roughly 
> 5KV
> spacing and (I'm guessing) maybe 600-700 pf.  It is turned by a 1 RPM gear
> motor powered by a two conductor control line or through the coax.  The
> control unit has a rocker switch to apply voltage for forward or reverse
> tuning (by reversing + and -) and the capacitor rotates freely without any
> stops.  You cut the dipoles to be about 5% long at the bottom end of the
> band.  If you find a cap and a motor you could build one easily.
>
> It is meant to go in one leg of a dipole or at the feed point of a 
> vertical.
> The cap is just placed in series with one leg of the dipole.  It works
> fantastic on 160 or 80.  Both my 160 and 80 dipoles can tune the entire 
> band
> with under 2:1 SWR.  This is going to be REAL important when the 80M phone
> band gets expanded.  I will try and make scans of the manual and post them
> on my WEB site and to BAMA (after the contest this weekend!).
>
> Mike, W1NR
>
> -----Original Message-----
> From: heathkit-bounces at mailman.qth.net
> [mailto:heathkit-bounces at mailman.qth.net] On Behalf Of BSugarberg
> Sent: Thursday, November 23, 2006 9:47 PM
> To: heathkit at mailman.qth.net
> Subject: [Heathkit] SA-2550 Antenna Matcher
>
> From the Heathkit book:
>
> "It is important to note that the SA-2550 is not a "tuner".
> It is a "matcher" designed specifically for use with single or multi-band
> half-wave dipoles, inverted-Vs, and 1/4 wave antennas.  It is not for use
> with 50 ohm beams, random wires, or balanced feedwire antennas."
>
> "To use the SA-2550 to its fullest requires you to lengthen your existing
> antenna by 5 to 15%."
>
> "Proper operation requires an external dual wattmeter or SWR bridge."
>
> "Very rare".
>
> 73, Bruce WA8TNC
> ====================
> Rick Brashear wrote:
>
>> Hi George,
>> I'm not familiar with that Heath number or capacitor.  Are you sure of
>> the number or component?
>> Rick/K5IZ
>>
>> George wrote:
>>
>>> I'm told that it is a Heathkit SA-2520 I'm looking for.
>>> Anyone know of one that is available?
>>> George
>
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