Antennas

[skier]

@-mjk-, Following our previous discussion, my work in radio has primarily been in VHF and up into microwaves, so the antennas have all been much smaller and have been verticals (ground planes), yagis, patch or dishes depending on frequency and application. Working at HF frequencies with long wire antennas is new to me, but very interesting. I’m seriously thinking about stringing out a 160m dipole, Carolina Windom, or even a simple random wire antenna. I’ve got a few acres with lots of trees, so space isn’t the problem. Getting the darn thing high enough to get a low take-off angle is my challenge. Also, the higher I go, the more I’ve got to deal with serious tree movement as well as getting the wire up there. And because we often have wind storms above 50MPH, and that I’m only 14 miles or so from the Atlantic, we somewhat often have hurricane force winds during the warmer weather and the upper parts of my trees move a lot at those times. I like the idea of a long wire being bent 90 degrees at some point in order to make my radiation pattern more omni like a Carolina Windom — at least, that’s what I believe that a bend might do at these frequencies by providing a quarter wavelength radiating element north/south, and after the bend, a quarter wavelength element radiating east/west (horizontally polarized, of course). Am I wrong?

That said, at 160 meters and likely even 80 meters, I suspect I can’t get the antenna high enough to keep my take-off angle as low as I’d like, such as in the 15 – 20 degree range. With the G5RV (35 feet AGL), I’ve been able to work Connecticut to Michigan going west and south to about Kentucky and the Carolinas, so perhaps 800 miles has been my limit. I don’t currently have an amp so I’ve only worked barefoot (100W on SSB) to this point. I eventually would like an amp in the 600 – 800W range, but not until I’m happy with my antenna. I believe I should be receiving much more in the evenings than I do currently and therefore want to straighten the antenna situation out first.

For gear, I bought a used Yaesu FT DX1200 transceiver on eBay and I’m very happy with it. It’s in like new condition and I’m positive it’s working well. For a tuner, I have a Palstar AT2K; it’s a manual tuner and I wanted that. I really think it’s a very good tuner so I don’t believe I have any problems there. I’ve used a VNA to determine the tuning of the capacitor and inductor settings for each band and have actually determined several for the 80M band because it’s so wide. At these settings I load into the G5RV with an SWR of 2:1 or less (mostly less) across all the bands up to 6M.

So that's my first question, and you're the first broadcast engineer that I've met, so I'm selfishly trying to learn from you. (Yes, that’s bad news because I have more questions.)

 

[-mjk-]

Jerry, 160M is a bear because it really is very close to the broadcast AM band. The G5RV only works on 160M with the leads shorted and the G5RV, although an excellent design, really has to be up in the air, in the clear. I have quite a bit of experience on 160M contesting and I'll give you some recommendations. 80M operation can benefit from the 160M experience.

Rule #1 on 160 Meters: A good 160M transmit antenna is not necessarily a good receive antenna. For contesting, Grady Moates (loudandclean.com) built us a matching network for WILD's 259' vertical (a 5KW daytimer at that time). John, WN9T made a 2 wire switchable Beverage antenna, and Steve NQ1F made a bandpass filter for the Beverage because we were in a very high RF environment with several other AM broadcast stations nearby. We used a TX/RX relay to switch between the 2 antennas. We worked stations all over Europe and South American on 160M with 100 watts on CW.

I suggest that you consider a design that will work with ground effect rather than be hindered by it. I understand that your trees sway around in the wind in the upper parts, but there is a height that is stable, and would make a good antenna support. I suggest that you check out a rhombic antenna. This is simply a wire antenna with a termination resistor at the far end. It's cheap and very easy to deploy and test. Being only wire, if it doesn't work that well, it's not like you put up a tower and now you can't use it.

The other thing you may want to look into is making some kind of a hybrid vertical, like a folded monopole, or one of those coax antennas that use coax cable for the vertical radiating element. The interesting thing about a coax antenna is that is has both inductive and capacitive properties and that simplifies the matching network for those low bands.

That should get you started on the 160M trail!

 

[skier]

MJ, good stuff - thanks! And I will check out loudandclean.com.

It's also interesting that you mention verticals. I actually like verticals a lot because of my ground plane experience. What I don't like is the need for 16 - 32 radials, or some such number of 50 or more feet each buried a few inches in the ground. Supposedly, using many radials reduces the chance of omni-directional inconsistency that can be caused by using fewer radials that are not straight nor uniformly spaced around the vertical's base, which makes sense. Most ground planes have only four or five radials and that works because they're placed very accurately by the manufacturer rather than some nitwit trying to dig lots of straight channels in the ground for long stretches. And here in New England, I live in a glacial moraine and there's no way said nitwit can dig more than a few feet without hitting one or more big rock(s) that require the power of a backhoe to remove.

So that brings me to a second question: if I put up a 1/4 wave vertical, whether coaxial, a wire in PVC pipe, or a long length of copper tubing coupled section to section for proper length and properly guyed, etc., could I get past the need for radials by using a counterpoise for the other quarter wave? Running one counterpoise of any length would be much easier, and I can place it for the directional properties that I want. Normally, we can use a vertical 1/2 wave antenna for its fundamental and its odd multiples. I could easily and fairly inexpensively put two or three verticals to cover the bands on my property and far enough apart to minimize interaction. And if I remember correctly, verticals are less sensitive to being close to ground than dipoles/dipole antenna types regarding of take-off angle. I've been wanting to try this, but because the G5RV took significantly more time to get up in the trees and presented more hassle than I expected, I'm wanting to vet my design approach before embarking on the construction time.

 

[Arjan P]

Love this radio talk.. But I'm also glad I'm teaching HF in aviation, where the HF antenna is a fixed length and has a coupler between itself and the xceiver. I'm already glad some students know the basics like 1/4 wavelength.. (but then, they have more to worry about than just radio)

 

[skier]

Wow! That's cool! And I also find it really cool that others here are finding that we share additional interests other than music and recording. Are you a pilot Arjan?

 

[Arjan P]

No, I teach ground engineers in commercial aviation, so HF is one of the subjects (as is VHF and Satcom).

 

[skier]

Wow, this is crazy. One of the reasons I have a GROL (General Radio Telephone License) is because it was needed here in the U.S. before the mid 80s to be an engineer or chief engineer in radio or TV broadcasting – that was something I wanted to do. MJK recently revealed he has the same license and actually did work in broadcasting. But that license was also needed to install, repair, or modify any kind of transmitter, and is still required to install VHF radios and radar on ships and on planes. It is also required for any kind of work on plane avionics and I was involved in all these activities on boats and planes in the past. Ironically, the only situation the license did not and still doesn’t cover is the building or servicing of Ham equipment – for that one needs a Ham license.

I know I stated this several times in the last two days, but I’m still amazed how the paths of interest for several of us are crossing in these areas and we never knew it.

 

[-mjk-]

I'm out in the car so I'll have to give you a more detailed response later. Basically, a quarter-wave vertical requires a groundplane and there's no getting around that. However, a half-wave vertical, although not completely ideal, is ground independent.

 

[-mjk-]

@skier Jerry, 1/4 wave ground plane antennas are what you would use when you are tight for space. There is no advantage to using a 1/4 wave unless you want a "skywarmer". The optimal wavelength for an HF vertical is a 5/8 wave because of the takeoff angle. In either case, you need a ground plane. In the 80s we learned that the typically unbalanced vertical system is in reality, a 3 pole system consisting of the vertical radiating element, the ground system, and the earth. The better the coupling you have with the earth the better the driven element works (with our present understanding of physics). The MFJ company used to sell a "ground tuner" (or something like that) for tuning a counterpoise or a grounding lead from a significant height above ground (like an apartment or an attic radio shack). They claimed that you would be able to toss a piece of wire out and tune it for the band of interest. In practice it doesn't work very well. Anomalies in the ground system will result in directionality - which may be desirable and may also be leveraged when you build your system.

Since you have the technical chops, it's only a matter of time involved, but, there are 2 things I would be inclined to try if I had a situation such as you described:

Trapped verticals in an array.
Multiband directional sloper array.

The great thing about the ham bands is their harmonic relationship. So, you could build 3 or 4 trapped verticals with multiband capability, and space them at the longest wavelength you can manage. Then you could build a phaser network to steer the signal. That would be way cool, but it would take a lot of time to get it all right (and a lot of math!).

The sloper array design already exists. You need a support structure, but it's basically a number of lengths of RG58 (I think the design calls for 8 radiators) that slope down from a central point on the tower and fan out equidistant around a circle. The shields and inner conductors are shorted on each of the radiators and there is a switching/matching network that not only changes bands, it also switches the directionality. If memory serves, it's 10M through 40M. My friend John made one years ago and he said it worked great.

It going to be interesting to see what you come up with Jerry!

 

[skier]

@-mjk- I really like the idea of the Multiband directional sloper array - let me research that. I actually would like it to work from 160M up, but that likely would require some really high center support and it'd make a dandy lightening rod - that aspect doesn't appeal. But being able to rotate the gain direction by changing the element phasing is very appealing.

I've considered trapped verticals and trap dipoles, but I don't like the losses incurred by the traps, so I think I prefer to go a fan dipole instead. And a local Ham I met when taking the Extra exam together tried a Carolina Windom for 160M up at a field day several weeks later and loved it - he said he couldn't believe how well it worked; that's why it's another design I'm considering.

A 1/2 wave or 5/8 wave vertical would be 260 feet and 325 feet high respectively and not only would it be a monster (and lightening attracter), the FCC limits us to 200 feet AGL, so I can't do that for the lowest bands. I think I'm down to deciding between sloper array, the fan dipole, a 160m dipole, Carolina Windom, or a simple long wire antenna, and I don't have a lot of faith in the long wire, but it's easy to test. Another option I perhaps should decide first is if I should drop 160M. 80M is too valuable, so I have to have that, but I don't get any reception on the G5RV for 160, so I don't know what I'd be missing. While I wouldn't try transmitting on that band using the G5 without combining the internal lead and shield of the coax as you mentioned, I still would have believed I could receive well enough to ascertain how much it's used, but I don't get much on that band using the G5.

I'll let you know what I find over the next week or so and what I decide. I also will want to later chat about an amplifier, but I want to get the antenna right first. I'm thinking of something in the 600 - 800 watt range. I'm feeling that going full power wouldn't get me much more than a higher electric bill. I mean, 3dB isn't much more power and that's also only half an S-unit. But going from 100W to 600 or 800W should make a vast difference. Currently, I've tried responding to many CQs that can't hear me even though they're coming through like a ton of bricks on my end. Just getting a better antenna up could make a big enough difference that I might not need any amp or could use something smaller - don't have enough metrics yet to decide.

Thanks again for the counsel!

 

[-mjk-]

You could try a rhombic with a terminating resistor for 160M. A tuned random wire is also an option. Wires are cheap and easy to play around with.

 

[skier]

Actually, the issue isn't so much the design as much as getting the antenna up to the requisite 50 - 70 feet. I've used ladders, fishing weights on a string thrown over, bow and arrow with string shot over, a drone, and recently, another Ham offered me use of his spud gun. The drone works well on a stand-alone tree, but a lot of this is on the edge of the forest that surrounds my home. The drone would get caught up in the branches of the trees beside and behind whichever one I'd be flying around.

The trees on my property are tall, generally between 80 - 110 feet above the ground, so that leaves some pretty sturdy limbs at the 50 - 70 foot height. No, the problem is how to tie/secure the ropes holding the insulators that connect to the outside, free ends of the antenna. I've considered renting a cherry picker (bucket lift), but the places around here want $300 - $400 a day and I find that price to be obscene. And securing the ends without it is a long, laborious affair. That's why my current G5RV is not set up as a flattop dipole, but as an inverted V so I can reacg the tie points with a 16 foot ladder.

Coincidentally, I was reading about the rhombic last evening, both terminated and unterminated. I think that or a skywire loop is where I'm headed. Both are simple, yet very effective across the bands. The rhombic can provide some good gain, but at the expense of being a fixed directional. And while the resistive termination broadens the bandwidth nicely, it has to be a non-inductive resistor, and that would be hard to find or make in a 1kW size (if I consider an amplifier later). It might even be hard to buy or make a smaller 100W size if I stayed barefoot.

Like most things in life, I've found antennas to be compromises across the range. Regardless, I much appreciate your suggestions! I'm getting close to a final decisions. As for installation, that'll have to wait for a change in weather. We got 12 inches of snow yesterday, more due tomorrow, and supposedly a big storm on Friday; and that's just for this week.

 

[skier]

Now, next question: Once I have my antenna situation RADICALLY IMPROVED, I plan on adding a 600 - 800W amp. I normally prefer solid state rather than tube, but not in this case. I'm concerned that if I mis-adjust the grid or plate drive/load adjustments or if the SWR goes too high for any other reason, such as an antenna line break, that I will kill the transistor finals. While tubes are not invulnerable, they certainly can take a "hot supper" for a short time and come back for more. Conversely, transistors just die instantly with heat or high-voltage transients. They are physically much hardier than tubes, but eminently more fragile electrically.

Any thoughts?

 

[skier]

Oh! Forgot to ask: There are many brands of amps, some I know had good reps historically (Drake, Hallicarfters, even Heathkit), but they don't exist any more except in the used market and I don't know the newer brands. Ameritron appears to have the widest selection and price points, but many Hams don't like them. They're owned by MFJ and many Hams refer to that company as "Mighty Fine Junk!" - Not exactly a ringing endorsement.

@-mjk- As always, any wisdom you can impart is greatly appreciated. And @Arjan P , now that I know that you, too, know more than just a little about radio communications, I'd greatly appreciate any wisdom you might share. Other sagacious souls advice who have hitherto remained quiet are also implored to share their counsel. What I don't know about this topic is a lot. (actually, many topics...)

 

[-mjk-]

I met Martin in the 90s and he's a good guy. MFJ is kinda like the Behringer of ham radio. Love them or hate them.

You could build a tube amp with broad enough bandwidth to be a "no tune" amp and only switch bands.

There are a lot of those old Heathkit amps around. Just have to go to the hamfests. I used to go to Deerfield every year up in NH. HRO usually has used gear - I sold some stuff through them.

Many newer solid state amps are bulletproof. Yaesu makes a couple of them that will work with your radio very well.

The AM radio band is rapidly changing over to digital transmitters. I bet you could find an old Gates 5kw for almost nothing.

 

[-mjk-]

Jerry, if you put up a tower, you could install all kinds of stuff on it. A huge multiband yagi like the Mosely (I did an install once with WN9T - amazing antenna), with a vertical on top. Then you could slant-wire feed the tower for 80M and 160M. Not to mention U/VHF yagis for the local repeaters. Maybe even your own repeater.

Here in Taiwan we don't have snow but we do have typhoons. But my ideal would be a big Quad, 40M through 10M.

 

[skier]

Because we have a move to Colorado on our horizon, I'm going to wait on the tower, but I agree with your idea.

As for Martin Jue (never knew his name before), I'm not sure why their equipment is derided so much by some. In researching Yaesu, it appears they only sell one amp these days, the VL1000. I don't feel that a full kW or even 1.5kW will give me much reach beyond 6 - 800W, and even more, it sells for over $4,000 - I don't want to spend that much. I will buy used for a more reasonable price and do like that I can much more easily replace tubes in the future than power transistors, though they could last longer if they're adequately protected.

As for your idea of a used gates - that's positively inspired! That is a great idea I had never considered. I need to research that and see if I can get one that's working at a reasonable price. Thanks much for that idea!

 

[Arjan P]

And @Arjan P , now that I know that you, too, know more than just a little about radio communications, I'd greatly appreciate any wisdom you might share.

Well @skier I would, but I have absolutely no experience in building antenna arrays or amplifiers or other radio setups. As a kid I built an FM transmitter and pretended to have this 'illegal' station but I guess it had no more than a 200m range (and lots of mirroring!) - so I won't be of much help here..

 

[skier]

No problem Arjan. Thanks for taking the time to respond.

 

[-mjk-]

@skier I can ask my friend Grady if he has any leads on an old broadcast transmitter, if you like.