Re: Antennas: Best Mini-Whip ??


jdow
 

When you guys comment about lower noise or higher noise is that in relation to received signals or simply "what the S-Meter says?" The former matters. The latter emphatically does not matter.

{o.o}

On 20210918 06:07:37, Ken Sejkora wrote:

I should also mention that at the old house, I was not using common mode chokes, and was getting good results.  At the new house, I installed the Mini-whip without CMCs, and it was virtually useless due to the high levels of noise.  I had noticeable noise reduction with the CMC at the antenna end of the cable, and another drop when I installed another CMC at the receiver end.  I even installed a third CMC in the basement between where the outdoor coax couples to the run of indoor coax that runs to the office/radio room.

 

Even with all of this effort, the Mini-whip is only “okay”, but not very good.  I put up a 70-ft random wire about 25-ft above the ground, fed through a 9:1 unun matching transformer.  Although this still picks up the interference from the solar panels, its noise levels are considerably lower than the Mini-whip.

 

Given my success with common-mode chokes, and the successes had by others with CMCs, I’d encourage you to at least try CMCs to see if your noise levels improve.  Although you can get CMCs commercially, I wound my own using small diameter RG-178 coax wound on ferrite toroids.  I was able to get 30-turns in the toroid, which gave me about 22 milliHenry of inductance.  Paul, W1VLF, has some good YouTube tutorials on making and using CMCs.  Here’s a link to one of them:

 

https://www.youtube.com/watch?v=dcXq6u64HXg&t=14s

 

Check out his other videos as well.

Ken

 

From: Ken Sejkora
Sent: Saturday, September 18, 2021 08:41 AM
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Antennas: Best Mini-Whip ??

 

Interesting discussion.  I’ve been using an active Mini-whip antenna for several years.  Two years ago I moved from one house to another.  At the first house, the miniwhip was located about 50-feet from the rear of the house about 20-ft above the ground.  The antenna performed very well at that location, with good SNR values from 20 to 30,000 kHz.  I should mention that at that house the AC utility lines were above-ground lines about 75-ft from the front side of the house.

 

When I installed the miniwhip at the new house, I placed it about 100-feet from the house, about 30-ft above the ground.  The antenna fed back to the house with quad-shield RG-6 coaxial cable, with common-mode chokes on both the antenna-end and receiver-end of the cable.  At the new house the utility lines are buried, as opposed to above-ground lines at the old house.  Adjacent neighbors are the same distance (minimum 300-ft) as the old house.  Despite these site characteristics that would appear to be “better” than the old house, the noise levels were considerably higher, and SNR ratios noticeably poorer.  One thing that is different about the new location is that most of the houses in our new neighborhood have solar panels on their roofs for generation of electricity.  The inverters used in such systems to convert DC power from the panels into AC power to feed the utility lines are notorious for generating noise, similar to that of switching-mode power supplies.  After sunset, the noise levels do drop, but still are higher than the old location.

 

Bottom line – your mileage may vary with having success with the Mini-whip.  Like they say in real estate… LOCATION, LOCATION, LOCATION!

 

Good luck.

 

Ken – WBØOCV

East Falmouth, MA

 

 

 


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