Mounting Inverted V Under A99 Vertical

[kaosfm]

I wanted to get some thoughts as to a proposal. I built a 2-element fan-dipole with one element tuned for 11-meter use and the other for 10-meter use. While my 1/2 wave vertical (A99) works quite well for both local and dx contacts on both bands, I would like to have the option available to switch to a horizontally polarized antenna on demand via a 2-way switch-box in the shack.

I have already established in my other thread that the A99 benefits nicely from the addition of 1/4 wave radial elements. What are your thoughts on mounting the inverted-v dipole directly below the feedpoint of the A99 vertical? This section of mast is actually made of wood, so that mast interference at the current-maxima of the dipole would be minimized. The inverted v features a choke balun at its feedpoint to prevent feedline radiation.

My thinking is that while I am operating the A99, the slanted legs of the dipole will effectively be seen as additional radial sections and not significantly interact or detune the A99 vertical. While operating the inverted v, I would suppose it would interpret the A99 vertical as if it were a section of mast above its feedpoint. As a final bonus, the inverted V elements will further "guy" the mast. It's a win-win in theory. In practice, who knows. I figured someone here has either attempted something like this or knows someone who has (and whatever their experience was).

Your ideas are much appreciated...

 

[wavrider]

It will work.

How good? You will have to try and see.

You may want to look at delta loops, use some more wire and get some gain over a dipole.

 

[kaosfm]

It will work.

How good? You will have to try and see.

You may want to look at delta loops, use some more wire and get some gain over a dipole.

Awesome! The experimenter in me simply has to find out. I think I will lower the mast this weekend and hook up the inverted V. You're correct in that ultimately trying things out is the only proper way to address the question at-hand. Thanks for the input.

 

[Robb]

Awesome! The experimenter in me simply has to find out. I think I will lower the mast this weekend and hook up the inverted V. You're correct in that ultimately trying things out is the only proper way to address the question at-hand. Thanks for the input.

It can be interesting to use a vertical and a horizontal antenna individually. With an antenna switch between the two antennas, you can hear stations that the other antenna cannot hear.

Me thinks it is best to have both . . .

 

[wavrider]

Awesome! The experimenter in me simply has to find out. I think I will lower the mast this weekend and hook up the inverted V. You're correct in that ultimately trying things out is the only proper way to address the question at-hand. Thanks for the input.

11m Antenna Building Instructions on the Internet — Foxtrot Lima

Dual Delta Loop for 10 and 12 Meters

A couple links for delta loops.

I have two co phased delta loops spaced .625 WL apart, they work fantastic on 10 meters, 11 also.

Use the vertical for local and dx then go to the delta loop and as ROBB said you can hear what you have been missing.

 

[Lil'Yeshua]

Cool! I'm wanting to do the same thing.

 

[kaosfm]

Well I couldn't quite wait, so I went ahead and gave it a go. There appears to be no negative interaction between the two antennas despite their proximity. I suppose if they were actually co-phased, it would be another story (and likely a disaster). The only problem is, I cut the dipoles to standard electrical length using the 468/F equation. I didn't realize until I put it up that you have to downscale inverted V designs by 4-5% to make them resonant. For now, they appear to resonate too low, i.e. the 10-meter length element is actually resonating right below the 11-meter band and the 11-meter element is resonant at the edges of the 12-meter band up into the 25MHz range. I will need to trim the elements and it is a pain to put up. It's worth it though!

Just scanning through the CB band tonight, practically no one uses horizontal polarization. Signal strength drops off several S-units in most cases. However, the amount of noise on the band is nicely reduced with the inverted V, which is what theory suggests will occur. It may still prove beneficial for DX work during the day since polarization gets quite skewed bouncing off the ionosphere and the angle of incidence for the inverted V could prove superior to the vertical in some cases. I spoke with a ham in Brazil today @ 28.4 MHz using my A99, but it was before my experiment was in place so I couldn't switch back and forth between the antennas. Tomorrow perhaps I will get another chance.

For reference, I am using 14 AWG insulated speaker wire for the dipole elements -- soldered directly to the stripped conductors of some RG6 Quad-Shield. It's cheap, low loss, and a good match for the dipole. I got a 1:1 match on some freqs. The area below the feedpoint has a 5-turn 4.25 inch diameter choke in place to prevent feedline radiation. It helps, but it doesn't solve the problem entirely. I think I may consider buying an actual MFJ balun or something of the like...

 

[Lil'Yeshua]

Pics please.
Actually,I was wanting my horizontal antenna to be circularly polarized or perhaps in a driven/director beam configuration mounted on it's own mast away from my A99 instead.

 

[wavrider]

Most of the DX on 10 and 11 will be during the day time.

 

[Robb]

Well I couldn't quite wait, so I went ahead and gave it a go. There appears to be no negative interaction between the two antennas despite their proximity. I suppose if they were actually co-phased, it would be another story (and likely a disaster). The only problem is, I cut the dipoles to standard electrical length using the 468/F equation. I didn't realize until I put it up that you have to downscale inverted V designs by 4-5% to make them resonant. For now, they appear to resonate too low, i.e. the 10-meter length element is actually resonating right below the 11-meter band and the 11-meter element is resonant at the edges of the 12-meter band up into the 25MHz range. I will need to trim the elements and it is a pain to put up. It's worth it though!

Just scanning through the CB band tonight, practically no one uses horizontal polarization. Signal strength drops off several S-units in most cases. However, the amount of noise on the band is nicely reduced with the inverted V, which is what theory suggests will occur. It may still prove beneficial for DX work during the day since polarization gets quite skewed bouncing off the ionosphere and the angle of incidence for the inverted V could prove superior to the vertical in some cases. I spoke with a ham in Brazil today @ 28.4 MHz using my A99, but it was before my experiment was in place so I couldn't switch back and forth between the antennas. Tomorrow perhaps I will get another chance.

For reference, I am using 14 AWG insulated speaker wire for the dipole elements -- soldered directly to the stripped conductors of some RG6 Quad-Shield. It's cheap, low loss, and a good match for the dipole. I got a 1:1 match on some freqs. The area below the feedpoint has a 5-turn 4.25 inch diameter choke in place to prevent feedline radiation. It helps, but it doesn't solve the problem entirely. I think I may consider buying an actual MFJ balun or something of the like...

Simply not so. Perhaps bad timing on your part. There are a lot of guys out there who use Yagis. I do, and I know some others that do. Try again.

 

[W5LZ]

A few things just for information.
That 468 number is never exact, always a slightly too long figure for a 1/2 wave length. An inverted 'V' antenna typically is slightly shorter than a 'flat-top' dipole, that's also normal. To 'skootch' the thing closer to where you want it just shorten it an inch or two. That's not all that unusual, it's just part of the normal tuning procedure. Any antenna that's not very high (meaning fairly 'close' to dirt) will have a slightly shorter resonant length than the formula gives. That 'magic' number is going to be slightly too long no matter what height above ground it ends up. That's certainly better than it being slightly too short though. Doesn't matter if it's an inverted 'V', 'flat-top', or some other odd shape. There's only two good reasons to use an inverted 'V'. One is you don't have the ability to mount it 'flat', and the 'biggy', making the 'angle of the dangle' less than 180 degrees lowers the input impedance (closer to 50 instead of 75 ohms). An inverted 'V' antenna is still a horizontally oriented antenna unless it's turned sideways (vertically). That "more vertically polarized" thingy is just another myth.
As far as those two antennas affecting each other, yes they will to some extent. Probably not all that noticeable, but it happens. Unless it has some substantial adverse affect, don't worry about it.
Using an SWR meter can ONLY tell you about impedance matching, it has NO ability to tell you anything about resonance. So, if you are worried about resonance find something else to use for that. Not a very 'nice' thought, but it's a fact, get used to it.
From what I can gather from your posts your antennas are doing about as 'normal' as they can get. I'm sure that if you put the effort into it you could make the 'numbers' more palatable, but don't expect any huge improvement, there just won't be. So, if it works, have fun with it!
- 'Doc

 

[Road Squawker]

.... The only problem is, I cut the dipoles to standard electrical length using the 468/F equation... I will need to trim the elements and it is a pain to put up. It's worth it though!...

don't do any cutting just yet,.. just fold the ends of the wire back on itself and then try it.

after you have it where you want it, you can cut it (or not cut it)

 

[kaosfm]

Hi All,

A couple of updates for everyone on this thread. I was able to trim the dipoles to resonance. To broaden the bandwidth a bit while maintaining low SWR, I recently acquired a MFJ-941e antenna tuner and put it inline. The results are excellent. I can tune it to a perfect 1:1 match on the entire CB band and maintain 1.5:1 or less on all of 10-meter from 28-29.7 MHz. I am seeing more issues with TVI though when using the dipoles compared to my A99 vertical. I don't know if a lot of common mode is coming down beyond the choke or if the inverted V design simply creates more RF energy in the region immediately below the antenna.

From a practical standpoint, receive on the CB band is almost always superior to that on 10-meter with the A99 vertical. However, on 10-meter, the inverted v parallel dipoles tend to equal or slightly out-perform the A99. I'm not entirely sure why this is the case since polarization is not maintained during DX communications. Perhaps the the interference rejection typical of horizontally polarized antennas is proving advantageous, or because more 10-meter signals are horizontally polarized to begin with and it still impacts the signal despite the atmosphere's tendency to shift the wave-form.

Below are a couple of pics of the install...