[Antennas]efficient antenna tuning

[Don Havlicek]

There was NO confusion on my part, just that your original answer lacked 
some clarity and correctness, as my post pointed out.
Do NOT put words in my mouth, nor try to interpret my thoughts, as I am 
able to express myself quite clearly in my old age.
Don
N8DE

DJED1 at aol.com wrote:

> 
>N8DE has suggested leaving the antenna alone and operating- while that  has 
>it's benefits, I thing the original poster was looking into how he could  
>operate over the entire 40M band without climbing on the roof to retune the  
>bugcatcher.  Since my comments caused some confusion with N8DE, I'll try  and 
>clarify for the benefit of all.
>In general, it is known in the technical community that an untuned  antenna 
>should either be tuned for a match to the transmitter at the antenna, or  using 
>a low-loss transmission line, at the rig.  Open wire line is commonly  
>recommended for a low-loss line.  The issue is that the loss on the line  increases 
>with SWR, even if you have a tuner at the rig so that the rig sees an  
>impedance match. 
> 
>In this case the coax loss is only about 0.4 dB for a matched line, but can  
>go above 1 dB for a SWR of 8 or so. (For N8DE's benefit, the SWR on the line 
>is  related only to the antenna impedance and the impedance of the coax.   A 
>tuner at the rig matches the impedance of the line-antenna combination to  50 
>ohms, but doesn't change the SWR on the line. Calculators for cable loss vs  SWR 
>are available on the net and in ARRL publications.)
>So the first choice of several posters was to put the tuner at the  antenna.  
>Costs about $200, and has about 1 dB of loss for the tuner and  0.4 dB of 
>cable loss.  I agree, and I use an ICOM AH4 tuner with a whip on  my portable rig.
>Given that the original requirement was for QRP and low cost, I considered  a 
>small QRP tuner at the rig, which may cost less than an AH4.  In this  case, 
>the cable dissipation will be more, depending on how high the SWR of the  
>antenna is at the ends of the band.  Even with a 10:1 SWR, however, the  cable 
>loss increases to only about 1 dB, with the tuner adding another 1  dB. So this 
>is the best tradeoff of performance and cost.  
>Finally, I suggested detuning the antenna if all that was available for  
>tuning was a capacitor.  To answer the question about series or  parallel would 
>require some assumptions about the antenna impedance and  some transmission line 
>calculations (remember Smith charts?), which I'm too lazy  to do right now.  
>however, the added cable loss make this a poor choice.
>So my recommendation is to set the antenna at the center of the band, get  an 
>inexpensive tuner and install it at the rig, and go have fun.
>Just my .02 based on 25 years as an Extra and 35 years as an RF  engineer
>Ed
>
>
>______________________________________________________________
>Antennas mailing list
>Home: http://mailman.qth.net/mailman/listinfo/antennas
>Help: http://mailman.qth.net/mmfaq.html
>Post: mailto:Antennas at mailman.qth.net
>
>  
>