What Do You Guys Think?

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ka3jjz

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Yeah, as I commented earlier, his 1680, plus all the junk showing up on LW from the MW band (which is a common problem) is all indicative of an overload issue. I believe he has a Wellbrook loop, and if it's pointed directly in the path of the MW station, it's very likely to be the cause of his issues, which is why I suggested turning that loop away. It's almost like 'looking down the barrel of a blowtorch'...

In addition, adding a LW filter wouldn't hurt either. The R71A is a very old receiver, and I wouldn't doubt that some components have drifted out of spec over time.

I hadn't thought of an unintended radiator, but you're quite right, under the right conditions it might rectify a RF signal that was strong enough. The problem is that it could be more than 1 joint, bolt or connection that could be doing this, and narrowing this down is likely to be a bear. Too, if you live in an apartment or condo, you have little control over the exterior.

MIke
 
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ka3jjz

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Ridge, if you do build the external RF control, put it in line with your Wellbrook. Since that loop is amplified, it's likely putting out so much RF into your radios that it can't handle it under these conditions.

That's one of the very few things I don't like about these kinds of loops - in situations like this, there's no way to remotely control the amount of gain.

Mike
 

ridgescan

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Like I said before, I need to put the R75 in place of the R71a in the livingroom on the 100' wire to see if indeed the R71a is prone to overload like this. I will try to do that in the next couple days. The 1680 getting 560 is what Mike said earlier-a 3rd harmonic 560x3.
This problem is at least twice as bad on the wire as it is on the loop.
BTW I have utility lines less than 20' from me, being on the third level of this building.

Here's a video I took this morning.
https://www.youtube.com/watch?v=0nLRu-WkkGs&feature=youtu.be
 

ridgescan

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Here's a bit of light reading for you, Ridgy. I think you can buy high-pass filters to block the BC band signals but this article shows how to make one.

www.dxing.com/tnotes/tnote06.pdf


Here's another one...

A simple homebrew high pass filter | The SWLing Post
Thanks Martin! Got through the first link-very good and well-explained in simple text. It looks like a wave trap for 560 and I think 810 also are in order for my situation. Otherwise that absorptive filter he explained may be helpful. Damn you guys are so smart and have vast RF engineering talent-I'm just a dummy radio geek who loves twirling dials:D
BTW, my wire goes like this: 45' from feedline running north, then bends and the remaining 55' the wire end points west. Do you think I have too much wire? Should I lopp off the 55' that ends to the west and just leave the initial 45'? One thing I know-that antenna is strong.
 
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ridgescan

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I took a couple photos of my antennas. In the first one, it shows the 100' wire feedpoint with 9:1 PAR transformer. This is mounted to an old stainless steel D130j mast that is grounded direct and mounted to a copper aerator pipe for water that I tested for electrical ground.


In the second one, the wire goes from that point all the way to the rear corner of the building then turns on that wood dowl mast you can see way back there mounted to a fire escape ladder, then goes left 55' to another mast out of the photo.
Also you can see the Wellbrook and the D130j on masts.
 

WA8ZTZ

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The spurs you are hearing are caused, as Mike has mentioned a couple of times, by a strong local station(s) overloading the receiver mixer and RF amp. An attenuator will help but the downside is that it also attenuates desired signals. From your location, trans-pacific DX is a real possibility and you will need all the sensitivity you can get. So, the solution is probably the filter route. For LW DXing, a low pass filter with the cutoff at the low end of the AM broadcast band (530). For AM BCB DXing, a wave trap tuned to 560 to reject that frequency. Place the filter right at the RX antenna input, use a double male PL-259.
 

ridgescan

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I switched out the R71a and connected the R75 to the new wire antenna. NO harmonic on 1680. Still MW stuff in LW but when I hit the ATT on the R75 it goes completely away. Does this mean the R71a is going south? It sure doesn't act like it as it runs just like it did when I got it back in '09. Gees now I am off to connect the R71a back in here in the bedroom onto the Wellbrook and see what it does.
EDIT: guess what-NO harmonic on the R71a on the Wellbrook. Very confusing. The 71a don't like that wire! OK so easy fix switching radios.
Here's a shot of the 71a back on the Wellbrook-note no ATT even needed!
https://www.youtube.com/watch?v=XnjPsUYOhtY&feature=youtu.be
So things come to mind like how you guys discussed that 560 could be riding into the 71a front end on power lines etc, well don't forget that the wire antenna's feedline is closer in the livingroom spot to those utility poles that run by my house, also it runs under and alongside that cable TV coax bundle on the roof. The Wellbrook's feedline is 20' away from all that. Also, the livingroom spot where the 71a was this morning is closer in proximity to the utilities wires where the bedroom spot for the Wellbrook is about 25' further back from them. No matter what, it would seem the R71a's front end is far more prone to saturation than the R75.
 
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majoco

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The answer is...it depends... If the R75 has got some better bandpass filtering before the RF amp or mixer then it may well have better rejection than the R71a. My HF receivers, old faithful Kenwood R2000 and the JRC NRD515 both have untuned octave filters, the Debeg 73713 has a tuned bandpass filter/preselector and my latest addition, an FRG7 has a preselector and they are all right at the antenna terminal where they do the most good. Some radios have so-called protection diodes at the antenna terminals so if your BC signal is so high as to start these things conducting on peaks then that will splatter all over the place. An antenna tuner at the receiver will act as a preselector too, so you might try that if you have one handy. It wont act as a true antenna tuner as you have already converted any weird impedances at the balun and coax cable.
 

ridgescan

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You're likely right on the R75 Martin, it is about 25 years newer that the R71a, probably better technology added since. I am just happy that both rigs are happy where they operate now:)
 

WA8ZTZ

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You have mentioned the location of the wire antenna's feedline a couple of times as running along with cable TV coax and also closer to nearby power lines. So, reroute the wire antenna feed away from all that stuff. Don't worry if it may require a longer path, at the frequencies you are interested in the loss in the extra length will be insignificant. It may take some extra effort but hopefully the results may be worth it.

btw, looks like the R71 and R75 use different IFs and conversion schemes
 

ridgescan

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You have mentioned the location of the wire antenna's feedline a couple of times as running along with cable TV coax and also closer to nearby power lines. So, reroute the wire antenna feed away from all that stuff. Don't worry if it may require a longer path, at the frequencies you are interested in the loss in the extra length will be insignificant. It may take some extra effort but hopefully the results may be worth it.

btw, looks like the R71 and R75 use different IFs and conversion schemes
Thanks WA8ZTZ-you know, rerouting the feed aint a bad idea, problem is that TV cable bundle runs the length of that side of the building one end to the other. Then it snakes down the side of the wall where the feedpoint is, so I'd still have to cross it. But I could run it indoors through the livingroom, through the bedroom then out where the Wellbrook feed runs. Something to think about. Hell I was running a 35' patch from the Wellbrook coax switch in the bedroom all the way out to the livingroom spot so why not right?
 

WA8ZTZ

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Well, you could give it a try as you suggest and see if things improve.
Sometimes you never know with this antenna stuff until you try it.
Let us know how it works out.
 

ridgescan

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Well, you could give it a try as you suggest and see if things improve.
Sometimes you never know with this antenna stuff until you try it.
Let us know how it works out.
Will do but honestly, since switching rigs with each other it's been fantastic and quiet. I aint in any hurry to mess with it now:)
Thanks for all the help here!
 

ridgescan

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Plus there's a nice bonus, I get Highway Patrol all across the bay area on the 42s very well on this antenna for some odd reason. Even clearer than on the scanner/d130j. I even backed the preamp off on each CHP channel to preamp1 for scanning on the R75 because the local one is so strong. Pretty cool!
 

WA8ZTZ

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Interesting, CHP still using VHF low band.

btw, nice catch on CFRX... usually a fair signal in here but only 250 mi away
 

ridgescan

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Interesting, CHP still using VHF low band.

btw, nice catch on CFRX... usually a fair signal in here but only 250 mi away
I'm glad they still do here, but what's even more interesting to me is how this big ol' wire can go that high and get them that good. I would think it would drop off at a lower point. I like hearing CHP on the R75 mated to a Boston center channel speaker better than the scanner because of the fuller "base" sound of their transmissions on it. It feels like you're listening to MIL transmissions....which you kind of are, them being "state troopers".
 
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