Johnny Novice to the rescue!

[N3DRB The Derb]

Mr. Novice slingshotted my antenna back up again today. 

A clone of the last antenna except it's got aircraft cable on both ends for support now. We're gonna be rockin in the free world. 

Thanks, Mr. Novice. 

[ve6pg]

...i shud get him over here tim...i think i have set a personal record this winter, fer ants. coming down...

..sk..

[N3DRB The Derb]

I'll be putting up a  40 ~ 50 tall mast/tower center support if it comes down again. 

I'm going to have to put up something else for 40 it seems. Matchbox wont tune the 75 M ant on 40. maybe feeder length is bad, too close to a current or voltage node. Gonna have to play with it. maybe just order a 40 meter version and be done with it.

this thing seems like the bomb on 75 as is, not sure I wan to modify it in any way. I'm going to put a RF ammeter in line today and see if my feeder current is hi, low, or normal. The feeder length was 100 ft, and I'm thinking measure the remaining wire and find out if I am somewhere around 62~66 ft feeder length. That would answer some questions.

[k4kyv]

If  it won't tune on 40, it is more likely that on that band the total dipole leg + feedline length comes out to be an odd multiple of 1/8 wavelength on that band, and the tuner is seeing midway between a voltage and current node.

If it is exactly at a voltage or current node it should tune to resonance very nicely, either in series or parallel tuning mode, with minimal reactance in the load.

[N3DRB The Derb]

you're right don..... Gotta start reading the handbooks so I can re-learn this stuff again.

It acts like a RF sponge on 75. Not sure I wanna mess with it.

[KA1ZGC]

Maybe a 30-ish foot vertical for 40? Should give you some nice low-angle energy, and could even be installed on a center support for the 75 meter ant. They shouldn't couple into each other too badly, either.

[K1JJ]

Maybe a 30-ish foot vertical for 40? Should give you some nice low-angle energy, and could even be installed on a center support for the 75 meter ant. They shouldn't couple into each other too badly, either.

Yep, I've been hearing some good signals on 40M outa verticals lately.

There's a KH6 in Hawaii who has a vertical on the beach with raduials into the water. The other night he was crashing in a S9+30. The USA guys were all commenting about his unusual ground conductivity situation...


But anyway, Derb, if you try a simple vertical, be sure to keep it at least 65' away from the  vertical portion of your 75M dipole's feedline. They can couple easily and make the two antennas perform the same due to shared RF.   

Even a 32' wire hanging from a tree top with some radials on the ground (or elevated) will work for you.

Though, if your new dipole is 50-60' high on average, that ant will be hard to beat on 40M DX.... even for the vertical unless the vert is an exceptional system that REALLY has low angles without loss.   In modeling, you will find the biggest advantage the vertical has is in angles below 10 degrees take-off or so. These angles are pretty useless for the most part on 40M and are extremely hard to get w/o attenuation from nearby obstructions and good Earth ground out many wavelengths.

It's hard to beat a high (1/2 wavelength - 65') horizontal dipole or Yagi on 40M.

T

[N3DRB The Derb]

its only up about 45'. Thats the limit for my trees here. Last night the Uncle Ed show was on so I didn't bother trying it out. 

Should be on later for whuts fer dinner net unless I cant get all the boards back in the Yaesu in time, I'm finishing the all new electrolytic cap on every board job today and tomorrow. So far every single cap I've replaced has been bad to some degree, the worst having changed into a 1 meg plus or minus a bit resistor. None of them showed any outside signs of distress as of yet. I am hoping to find a few disgusting filthy leakers or bulgers with hideously distended bellies. 

[Mike/W8BAC]

Just My 2 cents worth, You might hang a 40 meter dipole from the same feed point as the 75 meter antenna. This setup worked for me for many years until I went to the W7FG doublet. Something to think about.

Mike

[K1JJ]

Just My 2 cents worth, You might hang a 40 meter dipole from the same feed point as the 75 meter antenna. This setup worked for me for many years until I went to the W7FG doublet. Something to think about.

Mike

Yep, that wud be my suggestion too, for coax.

I think Derb is using open line, so as-is he wud  pick up 2-3 db gain on 40M in the broadside direction. 

But even with openwire, if he wanted to maintain that broad figure 8 dipole pattern, an extra  pair of 40M legs wud work with open wire too.

The legs might even solve his antenna tuner matching problem on 40M.... hmmmm...

T

[Mike/W8BAC]

Yup, It's coming back to me now. I seem to remember some pictures of Derb's open wire feed line. This has me thinking something else might be going on like maybe a misplaced tap in the tuner?

How would you test the tuner? You would have to put a representative load across the balanced output and see if the tuner would match it. I think it would be worth testing the antenna as well. Any ideas T. I'll have to dig out my MFJ 269 analyzer manual to see if it will work on a doublet. I doubt it. At the moment I can't think of any way to test the antenna short of a TDR and a calculator.

Mike

[W3NP]

I'm going to have to put up something else for 40 it seems. Matchbox wont tune the 75 M ant on 40. maybe feeder length is bad, too close to a current or voltage node. Gonna have to play with it. maybe just order a 40 meter version and be done with it.
this thing seems like the bomb on 75 as is, not sure I wan to modify it in any way. I'm going to put a RF ammeter in line today and see if my feeder current is hi, low, or normal. The feeder length was 100 ft, and I'm thinking measure the remaining wire and find out if I am somewhere around 62~66 ft feeder length. That would answer some questions.

Glad you got your antenna back up Derb. FWIW - I am using the same antenna but with the full 100' of feedline (maybe a few feet short) and my KW matchbox settings on 40m are (tuning/matching) 17/10 at 7100 and 12/26 at the top of the band.
What you might try, and I have had to do this before on other antennas is to splice the piece you cut off back in and just try and "lose" the extra length outside somewhere (zig zag it about). You could even experiment with it inside at low power to find out if that will do the trick.
Dave

[K1JJ]

What you might try, and I have had to do this before on other antennas is to splice the piece you cut off back in and just try and "lose" the extra length outside somewhere (zig zag it about). You could even experiment with it inside at low power to find out if that will do the trick.
Dave

That sounds like the easiest thing to try right now.  Derb will probably find a compromise match between 40 and 75M in feedline length. Sounds like worse case is he will need to add or subtract in 17' maximum feed line to dial in 40M... probably less.

T

[w3jn]

My pleasure, DRB, and TNX fer the fine business feed afterwards.

My Flashbox won't toon my 75 ant on 40 either.  Not enough range I guess.  Perhaps a series cap in the link input winding might help?

[N3DRB The Derb]

It might, but I'm not opening that back up again      ....... 47 sheet metal screws... I'll get on 40. I'm thinking add some feeder n see how it tunes.

[Steve - WB3HUZ]

Glad you are back on with a full up antenna. A short loop of ladder line will probably fix the problem. If you have a knife switch, you can cut it in and out as needed. Some people actually tune their antenna this way.

http://www.w5dxp.com/notuner.htm

[N3DRB The Derb]

actually, i DO have a strapping -K-nife switch thanx to the mopman!!!!   I'll try that starting right now while I have some day light left. 


p.s. the 1947 handbook has similar information in it, also playing around with tuned stubs and such. In those days, the feedline length was considered as carefully as the flat-top.

[Steve - WB3HUZ]

You was LOUD on 3733 this afternoon. That antenna is working on 80 meters. If you have similar results on 40, you'll be the king of swing.

[KA1ZGC]

Just My 2 cents worth, You might hang a 40 meter dipole from the same feed point as the 75 meter antenna. This setup worked for me for many years until I went to the W7FG doublet. Something to think about.

Mike

Yep, that wud be my suggestion too, for coax.

I think Derb is using open line, so as-is he wud  pick up 2-3 db gain on 40M in the broadside direction. 

But even with openwire, if he wanted to maintain that broad figure 8 dipole pattern, an extra  pair of 40M legs wud work with open wire too.

The legs might even solve his antenna tuner matching problem on 40M.... hmmmm...

T

I was considering hanging a set of 40 meter radiators from the feedpoint of the existing 200' flat-top a while back (no switching or trapping involved). When I modeled it, I was suprised to find it didn't alter the pattern or the match on 75 enough to be concerned about.

The model showed a classic dipole pattern on 40, with a somewhat reactive, fairly low impedance at the feedpoint. Nothing a flashbox wouldn't handle.

I've since opted not to, because my northeast lobe puts a tremendous second-hop into Europe on 40, making it a great night-timer. In my case, that medium-angle energy would vanish in favor of high-angle stateside if I added those radiators, so I'll do something else for 40 meter daytime work.

Mind you, I have to; if Ashtabula Bill can't hear you during the day, you're not really on 40.

...for whatever that's worth.

[K1JJ]

I was considering hanging a set of 40 meter radiators from the feedpoint of the existing 200' flat-top a while back (no switching or trapping involved). When I modeled it, I was suprised to find it didn't alter the pattern or the match on 75 enough to be concerned about.

The model showed a classic dipole pattern on 40, with a somewhat reactive, fairly low impedance at the feedpoint. Nothing a flashbox wouldn't handle.

I've since opted not to, because my northeast lobe puts a tremendous second-hop into Europe on 40, making it a great night-timer. In my case, that medium-angle energy would vanish in favor of high-angle stateside if I added those radiators, so I'll do something else for 40 meter daytime work.

Hi Thom,

Looks like what you experienced is quite normal.

The only comment that confuses me is the last one about losing the medium-angle energy by adding the 40M legs.    Normally, if the added 40M legs are at the same height as the 75M legs, the vertical pattern will be close to without the added legs.  Only the horiz pattern would change.

Is this vertical angle change because you are modeling inverted vees for the 75M legs, causing a higher TO angle on 40M, and adding higher (average)  40M legs that then pulls the TO angle down?   There is also some vertical angle deterioration from using full wave elements on 40M too, but not too dramatic - only 10' of height's worth.  (hope you followed that poor description)


T

[KA1ZGC]

Tom,

What I've got now is a 200' flat-top up 35' at the feedpoint, fed with abt. 35' of 420-ohm balanced line, broadside almost exactly east-west.

Its pattern on 40, as it stands now, resembles a cigar with butterfly wings flying along a parallel (in other words, the cigar is oriented east-west).

With this pattern, the northeast wingtip faces Europe. Its elevation angle is about 50 deg. With current propagation, the first hop lands in eastern Greenland, the second hop covers from the Scandanavian countries to the Mediterranian. The null falls through northeastern Spain (from NW-SE), and the eastern lobe covers northern Africa.

With the 40 meter dipole elements added, those lobes disappear entirely, and the antenna has a more uniform dipole-esque kind of pattern on 40. It fills in my nulls nicely, but also sacrifices those lobes.

That's what I meant by my medium-angle energy vanishing. That was a poor choice of words on my part. Clearly "vanishing" is overstating it, but the pattern would be devoid of that nifty medium-angle lobe towards Europe.

At any rate, it's quite handy for working over the pond as it is, not so much stateside; so I'll probably be putting up another antenna as a 40-meter daytimer.

Does that sound a bit more rational? My previous description was a bit misleading.

[K1JJ]

Tom,

That's what I meant by my medium-angle energy vanishing. That was a poor choice of words on my part. Clearly "vanishing" is overstating it, but the pattern would be devoid of that nifty medium-angle lobe towards Europe.

OK, I see now....

When you said "medium angle,"  I thought you meant the elevation angle or TO angle.  You meant the horizontal azimuth angle instead. That does make sense considering the butterfly sidelobe wings.

It's semantics, but "horizontal beamwidth" would have set me straight... :-)

Probably a better pattern wud be a broadside figure eight directly on Europe using the 40M legs... assuming you can orient it right.  But ya do what ya gotta do.

I'm almost finished here with the new European 7el 40M wire Yagi at 80'. It's on a 160' tramline-boom.   After exhaustive work tuning the elements, I've got the f-b now at about 40db to the USA.  Technically, I could hold a Euro QSO with strong USA stations on freq and neither of us wud be bothered.  The real advantage was last night. With T-storms from the USA doing +20 over on the west Yagi, it was almost dead quiet to the NE. That's where the competitive edge lies. (receiving)   I'm outside today raising the end legs of the els into higher tree supports.

I just love 40M with the easy access to 1/2 wave above ground! (65')  One can do some wonderous things using just trees, cable, rope and wire.


T

[Steve - WB3HUZ]

Here's a 3D shot of the pattern. Cool looking. Seems there may be enough high angle stuff in that center lobe for some stateside work, but  I guess the proof is on the air.

[KA1ZGC]

Yep, almost identical to mine, except mine's multi-color! 

If you want to see something really neat, check the 7000 kc pattern vs. the 7300 kc pattern. Midway up the band, it crosses the line from broadside to endfire.

The issue with that pattern in the daytime is where the nulls materialize. I've included a VOACAP shot of typical performance at 9 AM on a July day with a 0 sunspot index. Not exactly the best bearing for a null from my location!

It does great overseas, though, so I don't want to mess with it. I'll take another approach for daytime operation.

In Derb's case, though, secondary 40 meter radiators might be just the ticket for 40.

[N3DRB The Derb]

that thang works so good on 75 I'm skeered to touch it.