[TenTec] ATU Performance & Results

[Paul Gates]

Did you have a good reason for using coax?

Paul Gates

> From: RMcGraw at Blomand.net
> To: tentec at contesting.com; TenTec_Eagle at yahoogroups.com
> Date: Thu, 7 Feb 2013 13:38:02 -0600
> Subject: [TenTec] ATU Performance & Results
> 
> At risk of stirring the proverbial pot on this subject, I launched into a morning project of seeing what the internal ATU would handle and investigate if anything could be done to explain why some get better results than others.
> 
> The antenna used for this test is a center fed 75M dipole some 50 ft high and having a natural resonance at 3.8 MHz.  Center feedpoint has a 1:1 current balun and the feedline is some 75 ft of RG-213.  The output of the radio is connected to a to a suitable cross needle SWR/Power meter via a 1 ft RG-8x jumper.   The antenna side of the SWR/Power meter is connected to a Current Isolator or UNUN being a product from The Wireman item # 8232.  This is basically a coax jumper of some 3 ft in length fitted with a series of #73 and #43 beads.  This jumper is connected via a barrel connector to the RG-213 feeding the antenna.
> 
> It is noted after the initial test and repeating same for reliability, I found the removal of the Current Isolator between the SWR/Power meter and the coax to the antenna did cause some noticeable to very large errors in the value displayed on the external SWR/Power meter.  Thus the value indicated on this meter were affected by circulating current on the coax feed line.  This is not surprising.  I have had some suspicion that these circulating currents may have some effect on the performance of the internal ATU as well.   A point not of concern was the time required to attain a match as I only check one frequency on each band.
> 
> The values shown below are:  
> Band.......Frequency........SWR as shown on the radio.........SWR value as shown on the external bridge with the Current Isolator in place 
> 
> These values are using the Eagle with its internal tuner:
> 160M..........1942.......No Match......>10:1
> 75M............3900.......1:1...................4:1
> 60M............5357.......1.5:1................8:1
> 40M............7100.......No Match......>10:1
> 30M...........10114.......1:1.................10:1
> 20M...........14325......No Match......>10:1
> 17M...........18135.......1:1................ 10:1
> 15M...........21290.......1.2:1................5:1
> 12M...........24995.......1.5:1................5:1
> 10M...........28402.......1:1...................4:1       
> 
> These values are using the Omni VII with its internal tuner:
> 160M..........1942........No Match........>10:1
> 75M............3900........1.1:1..................4:1
> 60M............5357........1.5:1..................8:1
> 40M............7100........No match.......>10:1
> 30M...........10114........1.1:1...............10:1
> 20M...........14325........2.5:1.............>10:1
> 17M...........18135........1.1:1...............10:1
> 15M...........21290........1.2:1.................5:1
> 12M...........24995........1.4:1.................5:1
> 10M...........28402........1.5:1.................4:1
> 
> So what am I to conclude?  The Eagle ATU matched 7 out of 10 bands and the Omni VII ATU matched 8 out of 10 bands.  And the use of the Current Choke or line isolator does make a difference.  I did go back and re-test on 20M and have no explaination for the difference observed between the two radios using the same procedure and equipment for measurements.
> 
> {I  hope these tables stay in alignment}
> 
> 
> 73
> Bob, K4TAX
> 
> 
> DISCLOSURE:   
> This is to inform all persons, I am a Tentec Ambassador and I receive compensation according to the Tentec Ambassador program.  In addition, I serve as a volunteer beta test person to Tentec for the Omni VII, Eagle and Argonaut VI radios.  I hold no employment relationship, no financial interests nor do I conduct any commercial business, direct or indirect, with Tentec.
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