Did you have a good reason for using coax?
Paul Gates
> From: RMcGraw@Blomand.net
> To: tentec@contesting.com; TenTec_Eagle@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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