[TowerTalk] SP7GXP antennas?

[W0MU Mike Fatchett]

You have to email them for current pricing.  Shipping is expensive as 
expected.  Shipped in rock solid pvc containers.  Our UPS driver was 
impressed.

On 10/21/2021 2:15 PM, Pete Smith N4ZR wrote:
> From another angle, I note that Remote Ham Radio and W2RE uses (used?) 
> these antennas at the Eastport, Maine station.  An after-action report 
> on how they performed and particularly how they stood up in a very 
> exposed location could be informative.
>
> Two things also puzzle me - I can't find any pricing information on 
> the website (that may just be me), and while GXP is proud of his 
> association with W2RE  and RHR, the link to W2RE on the GXP website 
> has expired.
>
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network
> web server at<http://beta.reversebeacon.net>.
> For spots, please use your favorite
> "retail" DX cluster.
>
> On 10/21/2021 4:00 PM, Larry Banks via TowerTalk wrote:
>> Are they mixing up dBi and dBd?
>>
>> 73 -- Larry -- W1DYJ
>>
>>
>> -----Original Message----- From: David Gilbert
>> Sent: Thursday, October 21, 2021 14:48
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] SP7GXP antennas?
>>
>>
>> I own an Optibeam OB16-3 tribander as well as an Optibeam OB2-40 shorty
>> 40.  I modeled both antennas in EZNEC+ using the published dimensions,
>> as well calculating the impedance of the short square tube transmission
>> line that connects all three driven elements on the OB16-3 and
>> calculating the inductance of the "hairpin" matching coil used on the
>> OB2-40.  My modeled patterns matched very closely the patterns that
>> DF2BO had sent me.
>>
>> With the help on K9RX, who at the time lived about 30 miles line of
>> sight distant from me (we both lived on elevated ground), I then
>> measured the horizontal pattern by rotating my antenna while he took
>> signal strength readings.  With him transmitting, I again rotated my
>> antennas and took direct voltage readings using the microvolt mode (no
>> AGC or other compression) on my K3.  In all cases the measured patterns
>> closely matched the Optibeam specified patterns.
>>
>> It is a fact that you can't get additional gain without changing the
>> pattern, and 2 db would require a pretty significant narrowing of the
>> pattern.  It is also a fact that the vertical pattern is predominantly
>> determined by height above ground for similar antennas.  My conclusion
>> is therefore that either DF2BO has understated the gain ratings for his
>> antennas, or that SP7GXP has overstated the gain ratings for his 
>> antennas.
>>
>> 73,
>> Dave   AB7E
>>
>>
>>
>> On 10/21/2021 7:38 AM, john at kk9a.com wrote:
>>> I have modeled some OptiBeam antennas and the published specs seem 
>>> accurate.
>>> Of course getting 2db more gain from the same boom length would 
>>> circumvent
>>> the laws of physics. I recently installed a 4el 40m OptiBeam on my 
>>> tower,
>>> the SP6GXP version is 37% lighter.
>>>
>>> John KK9A
>>>
>>>
>>> David Gilbert AB7E wrote:
>>>
>>> His 16 element 20/15/10 tribander looks like an almost complete copy of
>>> my Optibeam OB16-3, except that SP6GXP claims about 2 db more gain on
>>> each band and uses lighter weight materials.
>>>
>>> Dave   AB7E
>>>
>>> _______________________________________________
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>>>
>>>
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