The purpose of my project was to determine what SWR values each model
would and would not match. There was no intent to endorse or suggest
that one use coax for a multi band non resonant antenna nor to say it
would or would not work satisfactory.
The point being, the two internal ATU units perform almost identical.
Agreed, the ATU in the Omni VII {as well as used in other models} does
tuner faster than the one used in the Eagle. This fact was not a point of
consideration in my project.
As Rick so apply stated in a different response, the better approach to
an all band antenna is the use of an open wire balanced feed system from
a balanced tuner. Having used a balanced system for over 50 years in
both amateur and commercial SW BC applications, it is much easier to
install and maintain than the "old ham lore stories" implies.
In closing, discussions on feed systems an associated issues will be
better served on a different reflector or discussion group.
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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