[TenTec] SWR is a DUMB Indicator of Antenna Performance

[Brian Carling]

That's right almost like a dead short to RF in many cases I expect.

Best regards - Brian Carling
AF4K Crystals Co.
117 Sterling Pine St.
Sanford, FL 32773

Tel: +USA 321-262-5471




> On Sep 15, 2014, at 10:11 AM, "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de> wrote:
> 
> In addition, if the antenna (i.e. dipole) has a balun using a ferrite toroid
> and we try to match the antenna on a band for which it was not designed,
> with help of a matchbox, then there is additional loss in the balun, which
> often can be significant.
> 
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
> 
> 
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Bob McGraw
> - K4TAX
> Sent: Monday, September 15, 2014 4:01 PM
> To: k9yc at arrl.net; Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] SWR is a DUMB Indicator of Antenna Performance
> 
> It seems that here we fall largely to the victim of verbal semantics. 
> Almost every radio I've owned, as well as the related printed manual, gives
> the indication there is a place to connect "the antenna".  In fact, we don't
> actually connect the antenna but more correctly we connect the "feed line" 
> or "transmission line" to the equipment and it is that feed line or
> transmission line that is actually connected to the antenna.
> 
> In general the generic description we use, the antenna,  has to do with the
> radiating part of our station, via various interconnect means, being
> described as "the antenna" and thus any tuning, more correctly matching, is
> then stated as "tuning the antenna".
> 
> Yes, feed line loss due to SWR is a concern in many instances.  Many
> feedline materials or choices have very low loss when operating at a matched
> condition.  However we find the loss goes up rather dramatically when the
> feedline is operated at other than its design impedance.  One needs to
> consult the published charts and tables to determine the matched loss for a
> given type of feedline and then an additional table to add the loss value
> when the feedline is operated with some value of SWR other than a 1:1
> condition or matched condition.
> 
> What is frequently overlooked, we take a given feedline having a loss of 1
> dB per hundred feet in a matched condition and use that feedline in a
> condition where the SWR on the line is 10:1.  We then find the total loss is
> 1.0 dB plus the added loss due to SWR of 2.5 dB for a total loss of 3.5 dB.
> 
> 
> 73
> Bob, K4TAX
> 
> 
> ----- Original Message -----
> From: "Jim Brown" <k9yc at audiosystemsgroup.com>
> To: <tentec at contesting.com>
> Sent: Monday, September 15, 2014 1:53 AM
> Subject: [TenTec] SWR is a DUMB Indicator of Antenna Performance
> 
> 
>> 
>>> My Ten-Tec 238 tune my 80 double ext.zepp on all bands 160-10 with a 4-1 
>>> balun 182 ft of 400 ladder line then the 4-1 with 20ft of coax.
>> 
>> No, it doesn't "tune" your 80 double ext.zepp, it creates a match between 
>> the transmitter and the FEEDLINE that allows the transmitter to dump power
> 
>> into the FEEDLINE. How much of that power gets to the antenna depends on 
>> the mismatch between the feedline and the antenna. It's pretty common to 
>> lose 10 dB between the transmitter and an "all band" dipole. 10 dB is 90% 
>> of the transmitter power.
>> 
>> I can make my 80M dipole look like 1:1 on 30M to my 200W amplifier, but 
>> mismatch loss is determined by the match between the ANTENNA and the 
>> FEEDLINE, and I would be burning 180 of those 200W in the feedline.
>> 
>> Bottom line -- SWR is DUMB, STUPID, and USELESS as a measure of antenna 
>> performance. I can LOAD a lightbulb, but it's a lousy antenna.
>> 
>> 73, Jim K9YC
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> 
> 
> 
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