Flex in high RF environment - WWV

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As I've posted here now a couple times, our local club is sponsor a celebration event of 100 years of radio station WWV.  We will be operating for 5 days around Oct 1, 2019.  Please see www.wwv100.com for more info.

Today I did our first "RF test" in our proposed operating area which is less than 1/4 mile from the primary WWV HF antennas.   WWV runs between 2.5 kw and 5.0 kw on the HF bands.  The HF antennas are all verticals.

I took my Flex 6300 out to the site with no special filtering and plugged it into a simple 20m vertical with four radials.

The movies below show the results.  To be clear the antenna was only optimal for 20m.  Everywhere else I used an MFJ tuner to get it close.   I was surprised how well my little 6300 did with all that massive RF around!

But clearly we will need some good filtering.  And I'm hopeful that the higher end Flex like the 6600 might do even better.

40m was actually just fine considering WWV transmits 5 kw on 5 Mhz.   20m however was kind of lousy and probably partly due to the fact that my vertical was nicely tuned for 20m so we picked up WWV just fine even though the closest frequency would have been 15 Mhz.

Anyway I'll will post a few more videos after we do more testing but if any of you are concerned about how well your Flex Radio does near high RF, here is your proof.  I think with a little filtering effort we could operate any band.

6m however would be a challenge since it is the perfect multiple of the WWV 25 Mhz signal.

Mark - WS7M

160m:  https://www.dropbox.com/s/kx2hotc6j4717fh/AtWWV160mNoBandPass05-04-19.mp4?dl=0
80m:  https://www.dropbox.com/s/t2piy94zs5hyjw2/AtWWV80mNoBandPass05-04-19.mp4?dl=0
40m: https://www.dropbox.com/s/y3sxnbmuqm34ejl/AtWWV40mNoBandPass05-04-19.mp4?dl=0
20m: https://www.dropbox.com/s/fwfkd78p5ntedq0/AtWWV20mNoBandPass05-04-19.mp4?dl=0
17m: https://www.dropbox.com/s/8kciai8z0pofp9p/AtWWV17mNoBandPass05-04-19.mp4?dl=0
15m: https://www.dropbox.com/s/f9d0cu19brdnee7/AtWWV15mNoBandPass05-04-19.mp4?dl=0
10m: https://www.dropbox.com/s/u5i8ai6pc9obhws/AtWWV10mNoBandPass05-04-19.mp4?dl=0
6m: https://www.dropbox.com/s/mf3zloivkodywad/AtWWV6ZoommNoBandPass05-04-19.mp4?dl=0

I did not attempt 30m as WWV transmits 5kw on 10.000.  When I took at peak it was pretty massive.

We will do another round of testing with filters.

This image shows the relative position of my small vertical to the WWV antennas.  At the far left arrow is the 5 mhz antenna.  The other arrow indicate the various bands: 10 Mhz, 15 Mhz, etc.

Distance from my location to the antenna is about 1/4 mile to the 5 Mhz antenna. Less to the others.



This photo shows the antennas for WWVB (60 khz) directly behind my test location. This is the south complex.  Three 400' towers.  There is an identical north complex.

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Mark - WS7M

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Posted 6 months ago

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Mike, W8BE

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I listened to the 20 meter recording.  It sounded to me like I could clearly hear WWV ticking away. 
Photo of Ken - NM9P

Ken - NM9P

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What were your WNB, NB, and Preamp Settings?

I can imagine using WNB would cause major problems in that RF field. Same with NB.


Did you try turning Preamp to -10 dB? It might help a bit.


This is one situation where almost any of the other 6000 models might have an advantage over the 6300 due to preselectors and preamp improvements.

But still.... so close to 5KW and still usable is pretty nice!
(Edited)
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Mark - WS7M

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Hi Ken,

I left everything off.  The next test I will likely bring my 6600 and will try many variations.

I am thinking filtering is our key.  Not -10 db pre amp.  We want to work stations so we need a way to notch out the WWV interference.

I think the 6300 could actually do the job but yes I think a higher end unit would do better.  My 6600 will be next.

Combine that with some good filters and I think we are ok to go.

Yes WWV could be heard on many bands.
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Mark - WS7M

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Ken you should sign up to come and operate for us!
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Ken - NM9P

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I may do a few things like that in retirement. But remember, I will be in a preacher’s pension and won’t be rolling in the dough! (But won’t be poor, either).

I hope to join a few major contests at big guns in the SMC, too! I will only be two hours away from K9CT and others.
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Bill -VA3WTB

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Mark it would be interesting if you report on the 6600 as it has much better filtering. That may be all you need.
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Mark - WS7M

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Hi Bill, 

Yes 6600 will be next probably in about 3 weeks.  

Mark