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Date: Thu, 05 Oct 2006 20:38:16 -0700
From: Scott Tilley <sthed475@telus.net>
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Subject: Re: LF: miniwhip not so miniresults...!
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Hi Alan

The vertical and miniwhip are within 25' of each other.

Steve, VE7SL and I did some tests tonight to determine the extent of the 
interaction.

When one connects the vertical to a RX while monitoring the miniwhip on 
another RX the 'signal level' jumps up by many S units.  tuning through 
the 2200m band above and below reveals that the peak is shaped exactly 
like the Q curve for my vertical.  Inserting an isolation xfmr in the 
vertical feedline has no effect.  Disconnecting the antenna wire past 
the loading coil causes the signal level in the miniwhip RX to drop back 
to original levels.

But how does this affect Miniwhip performance?

I asked Steve to send a carrier.  I then monitored the signal using the 
miniwhip with the vertical connected to another RX.  Noise floor was 
about S7, Steve's signal when on was S9+ a dB or two...  Disconnected 
the vertical from the other RX and repeated.  Noise floor was S3 and 
Steve's signal peaked around S5 + a dB or two...  Assuming my S meter is 
fairly linear over the range it would seem that the SNR remains fairly 
constant.

Now, how does this affect the poor FT-897D intermod rejection?

The following surprised me at first...  Setup the FT-897D with the 
Miniwhip and connected the other RX to the vertical. I listened by ear 
to the result on the 897's speaker.  With the vertical plugged in the 
signal level jumped up as observed before.  However, the intermod level 
compared to the signal level was very low to not noticable with the rig 
set to the IPO setting (preamp off) with the internal ATT inline no 
intermod was detected. 

Hmmm....

I then removed the vertical feedline from the other RX and, bang, up 
came the intermod even with the ATT inline.  In fact, the intermod is 
the dominate signal in the speaker and swamps out the noise!  Ok,  So I 
took a stroll out to the vertical and disconnected the antenna wire at 
the top of the coil.  The results where the same.

Seems the Vertical and Miniwhip are interacting in a positive manner WRT 
intermod on the FT-897D. 

What this means WRT to reception of a DX signal I don't know yet.

73 Scott


Alan Melia wrote:
> Hi Scott how close are the two antennas and did you disconnect the vertical
> antenna, or detune it when receiving on the miniwhip?
>
> Cheers de Alan G3NYK
>
> ----- Original Message -----
> From: Scott Tilley <sthed475@telus.net>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: 05 October 2006 02:13
> Subject: Re: LF: miniwhip miniresults...?
>
>
>   
>> Roelof and other interested parties
>>
>> Last night I meet with some success with the miniwhip and noted some
>> interesting things about my radios.
>>
>> I compared the 'large' vertical (50') with my TS-440 as a receiver
>> against the FT-897D and the miniwhip.
>>
>> After sunrise back east where a large storm was brewing  the noise floor
>> dropped and up came  VY1JA on both setups.  I got far better signals on
>> the vertical  but surprising good signals on the miniwhip that was
>> sitting on the roof of my greenhouse.
>>
>> This evening I mounted the miniwhip on my 20' carbon fibre fishing and
>> stuck it up about 30' above the back yard in the same spot on the
>> greenhouse as I ran last night. Boom! Up came the local 'warbler'
>> believed to be a local PLC signal; however, so did the intermod to crazy
>> levels as observed before.  This time I swapped the RX rig to the TS-440
>> and the intermod for the most part disappeared.  Putting the big
>> vertical on the FT-897D resulted in good signals from the 'warbler'
>> without intermod at all anywhere within the narrow window of the high Q
>> system...
>>
>> Summary of results:
>>
>>     * Seems the intermod is mostly generated in the FT-897D as suggested
>>       by some. Therefore, I wouldn't recommend the use of a Miniwhip(or
>>       perhaps other active whips) and 897 to someone in an RF wasteland
>>       like mine.
>>     * Height and location in the yard greatly affect the performance of
>>       the miniwhip and appear to make or break its performance.
>>     * The miniwhip collects more noise then the vertical.  Different
>>       isolation methods do help but generally it appears to soak up more
>>       local noise, maybe more DX signal too ;-)
>>
>> I'm a believer. Nice work Roelof!
>>
>> 73 Scott
>>
>> PS - I hope to update the TIL grabber tonight to simultaneously post
>> both miniwhip and 'big' vertical grabs from here.
>>
>>
>>
>> Roelof Bakker wrote:
>>     
>>> Hello Scott,
>>>
>>> I am living in a suburban area, with plenty of electronic equipment in
>>> full swing.
>>> However, all cabling is underground.
>>>
>>> I have some interference from my own VCR on certain parts of the band
>>> which is propagated by the TV cable system running underground
>>> practically onder my mini-whip.
>>>
>>> I have had reports from people with power lines in the vicinity.
>>> Raising the antenna above the level of the power lines did help.
>>>
>>> 73 Roelof Bakker, pa0rdt
>>>
>>>
>>>       
>
>
>
>