[50mhz] 50mhz Digest, Vol 65, Issue 24

Sat Jun 27 18:47:41 EDT 2009

The modeling I did on that antenna in stock form as the original 66DX is 
10.84 dBi. That is the pre VB version.

About the best that can be done with 6 el on that boom optimized for gain 
and F/R is 12.1 dBi with 22-25 dB F/R over the lower 500 kHz. Adding another 
element brings the F/R to a consistent 29-30 dB over the same range. I used 
one and later a pair stacked of the modified 6 el for a few years.

IMO, designing for maximum gain and leaving the F/R fall wherever it may, 
usually at 15-20dB, can be a problem when there are local noise sources or a 
crowded band. I try for 30 dB + over 500 kHz and know it will be very close 
in the air.

Notice also that I specify F/R which is over the full rear 180*.  Using F/B 
can be very misleading.

Carl
KM1H

----- Original Message ----- 
From: "Dan Schaaf" <dan-schaaf at att.net>
To: <50mhz at mailman.qth.net>
Sent: Saturday, June 27, 2009 12:40 PM
Subject: Re: [50mhz] 50mhz Digest, Vol 65, Issue 24

> Hi Lance
>
> How did you arrive at the following gain figure for the HyGain
> HyGain VB-66DX        1.21    8.97  7.35  6.04 14.45  11.80  11.37  5.51
> 4.53  13.01  11.37  10.98     37.7   1.12:1
> The advertisement says 12.5 dbi which is approximately 10.3 dbd and the 
> boom
> is 27 ft 6 element.I was planning to buy this antenna, so I am curious 
> where
> you got the numbers.Best Regards
> Dan Schaaf
> K3ZXL   www.k3zxl.com   "In the Beginning, there was Spark Gap"
> ===============================
> NOBSKA
> www.nobska.net
> ===============================
> Cape Cod Instruments
> www.oceanbiz.net
> ===============================
> ----- Original Message ----- 
> From: <50mhz-request at mailman.qth.net>
> To: <50mhz at mailman.qth.net>
> Sent: Saturday, June 27, 2009 12:00 PM
> Subject: 50mhz Digest, Vol 65, Issue 24
>
>
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>> Today's Topics:
>>
>>   1. Re: Comparison Table of 6m Antennas by VE7BQH
>>      (Lance Collister, W7GJ)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 26 Jun 2009 16:07:06 +0000
>> From: "Lance Collister, W7GJ" <w7gj at q.com>
>> Subject: Re: [50mhz] Comparison Table of 6m Antennas by VE7BQH
>> To: Magic Band EME Group <magic at 6meme.com>, Amateur radio moonbounce
>> <Moon-net at list-serv.davidv.net>, PNWVHFS <PNWVHFS at googlegroups.com>,
>> rmvhf at rmvhf.org, newsvhf at mailman.qth.net, Western States Weak Signal
>> Society <wswss at mailman.qth.net>, 50mhzer's <50mhz at qth.net>
>> Cc: "G0LCS, Kerry Rochester" <kerry.rochester at gmail.com>, Peter G8BCG
>> <peter at g8bcg.org.uk>
>> Message-ID: <BLU121-DAV5655E9762315846AE2B9489350 at phx.gbl>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> I now have the proper web page up in place with the link to the above
>> table, plus
>> links to a number of the antennas included in the table:
>>
>> http://www.bigskyspaces.com/w7gj/6mTable.htm
>>
>> VY 73, Lance
>>
>>
>> Lance Collister, W7GJ wrote:
>>> Howdy!
>>>
>>> Over the last quarter century, antenna performance has improved
>>> dramatically.  Thanks
>>> to the development of computer modeling software, antennas can now be
>>> designed to
>>> provide excellent results.  Many older antennas are still in use around
>>> the world
>>> that were built using less sophisticated techniques.  A number of 6m
>>> operators have
>>> wondered if it is time to upgrade their antenna systems.
>>>
>>> There is no question that each operator has different interests and
>>> constraints.
>>> Some want to arrange various antennas to "fill in the nulls" in ground
>>> gain patterns
>>> so they can be assured of not missing signals coming in at certain
>>> angles.  Others
>>> want to increase maximum signal strengths while still fitting the 
>>> antenna
>>> in their
>>> garden.  And still others are interested in assembling an antenna system
>>> that will
>>> have enough free space gain to enable them to complete EME contacts 
>>> while
>>> the antenna
>>> is elevated (without any ground gain).  With the differences in how
>>> antennas are
>>> marketed and what specifications are published, it is no wonder that 
>>> many
>>> hams have
>>> expressed confusion when they try to compare antennas to determine what
>>> would be the
>>> best choice for their particular situations.
>>>
>>> Lionel Edwards, VE7BQH, is well known for his pioneering work in EME and
>>> his
>>> knowledge of antenna design.  His comparison table of 2m antenna designs
>>> has been a
>>> valuable resource for weak signal enthusiasts on that band.  Lionel now
>>> has
>>> generously put together a table comparing a number of popular 6m 
>>> antennas
>>> to help
>>> guide Magic Band operators on antenna decisions.  This table was
>>> painstakingly
>>> prepared to include the free space gain of each yagi with respect to a
>>> dipole, the
>>> optimum and 75% of optimum stacking distances for both two and four 
>>> yagis
>>> and
>>> resulting gain figures, and the SWR of a single antenna 150 kHz from the
>>> design
>>> frequency.  The SWR value provides an indicator of the "Q" of the
>>> antenna, and how
>>> likely it is to be affected by rain, ice and snow; the narrower the
>>> bandwidth of the
>>> antenna, the more susceptible it is to such detuning by the weather.
>>>
>>>   http://www.bigskyspaces.com/w7gj/6mAntennaComparisonTableByVE7BQH.txt
>>>
>>> Please join with me in thanking Lionel for graciously agreeing to
>>> undertake the very
>>> laborious challenge of preparing such a table.  I will also post a link
>>> on my website
>>> to the table for convenient future reference, along with links to more
>>> information on
>>> many of the antennas listed in the table.
>>>
>>> GL and DX! VY 73, Lance W7GJ
>>>
>>>
>>>
>>
>>
>>
>> -- 
>> Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8,
>> E51SIX)
>> P.O. Box 73
>> Frenchtown, MT  59834  USA
>> QTH: DN27UB
>> TEL: (406) 626-5728
>> URL: http://www.bigskyspaces.com/w7gj
>> 2m DXCC #11/6m DXCC #815
>>
>>
>>
>>
>> ------------------------------
>>
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>> End of 50mhz Digest, Vol 65, Issue 24
>> *************************************
>
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