Yes while I agree, please understand my objective was to determine the
ability of the ATU to match various loads. I made no point nor provided
any data regarding feed line loss or antenna efficiency.
If I choose to use a feed line with very low loss at high SWR values I
would have chosen a balanced open wire line.
73
Bob K4TAX
> Bob,
> While determining that your rig can match a non-resonant antenna and thus
> transfer some power to it, this discussion fails to address the question
> of antenna efficiency and relative field strength of the radiated signal.
> Coaxial cable is extremely lossy when the SWR on the coax line (which
> does not change regardless of what your internal antenna tuner is doing)
> is above 3:1. Thus, it will not be delivering significant power to the
> antenna on non-resonant frequencies.
>
> Thus, the best advice we should be providing is to recommend the use of
> resonant antennas when coax is the feed line of choice. If the
> installation can accommodate the use of either ladder line or open wire
> feed line, then a non-resonant multi-band dipole can be used with a wide
> range tuner located at the rig with minimal feed line loss in spite of
> the high SWR seen on the non-resonant frequencies.
>
> 73
> Dave,K2DP
> Sent from my iPad
>
> On Feb 7, 2013, at 2:38 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
> wrote:
>
>> 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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