re: a jary riged dipole out of 2 mobile ant's

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

I had an idea for an apt hf antenna that I posted a while back and I can't find it so I am posting my update.
On my 2nd story balcony is a tripod held down with 3 cinder blocks because the apt complex won't let anything be nailed or screwed to the outside of the building by the residents, not even Christmas lights. Only Dish Network and Direct tv are allowed on the roof.
Problem is how to mount the multi band mobile hf antenna that I have in the picture bellow without ground radials hanging over the balcony (the management won't allow that either). A friend told me to get a 2nd one of those multi band mobile antennas and set it up as a dipole. I don't have enough room on my balcony for 2 of them stretched out horizontally and I wanted to test the theory out before I spent $60. some odd dollars on a 2nd one of those multi band hf antennas. I tried it out on 10 meters with an old tunable cb mobile antenna that I had laying around. Both of the antennas are up at 45°. I connected the shield of the coax to the center conductor of the cb antenna and the center conductor of the coax to the center conductor of the multi band hf antenna. The ground side of each antenna is connected together with the 1/2" plumbing pipe that I used in the mount. The lowest SWR reading is around 1.7 to 1, and was around 28.56mhz. The band ends are close but not over 3 to 1. I even has a QSO into Redding ca on USB voice. RST was about a little under 4 by 7 both ways. I think this proves that with the 2nd multi band antenna that this idea will work on all bands that the multi band antennas were built for. Any feedback on this idea.

The link https://www.dropbox.com/s/p6aat1nuh1fdy6c/multi band hf moble antenna.jpg?dl=0

An exture note. On 80m at 3.975mhz the noise floor is so high I can barly hear anyone on the WARTS net even when the band is booming in. I don't know if the 2nd multi band antenna will fix that. During the QSO on 10m the noise floor was very low.

Update on this setup. I now have the 2nd multi band mobile antenna mounted up. On all hf bands (80 -10 meters) the instructions say to set the upper whip at 27 1/4" for 80 - 10 meters then use the jumper to change bands. I am getting a reading on my MFJ-269 analyzer of 1.2 to 1 at the very low end of each band tested. I tested 80 - 10 meters. This is without my MFJ-901b antenna tuner inline. Do I need to adjust the upper rod longer on each side to bring the low swr reading on each band more in the middle of each band? and ruffly how much do I need to move the upper rod by?

 

[SCPD]

I’m not sure exactly, if this is what you’ll find useful- but first-- as I understand your question, you want some type of couterpoise to work against your balcony mounted multi-frequency antenna…. And you have consider’d using a separate one as this counterpoise, but lack the room to mount it all. You have a good idea, except, as you said- not enuff room for both.
.
One thing you might consider is turning your balcony into a ground plane. I don’t know how large it is, but if you could ‘carpet’ it with a wire mesh- like hardware cloth---- mounting the antenna so the base is at the level of this mesh- this is very important-- will give you something approaching a ground plane style antenna. You want to make sure that mesh is all bonded together and it is as close as possible to the base of your multi frequency whip. We are not going for a resonate ground system here, just as good an RF return as possible. The nice thing about a balcony is that you will have an elevated counterpoise- it will minimize the Ground Losses.
.
As far as the length of the tuning whip?… good question: I know nothing about that particular antenna, though I am sure others here will give you advice. Lacking that, and due to the very short nature of the antenna in terms of degrees of frequency, whatever resonates it would be good with me-- ie: get the lowest SWR.
.
Good luck- hope that planted an idea or two
.
……………………CF

.
.
* we use hardware cloth for all sorts of RF related things- like that ground plane, or Faraday, static,RF shields- its not just for rodent control anymore…….sorry, (smiles)

 

[bharvey2]

I've set up a similar dipole with 20 meter ham sticks. One acts as the antenna, the other the ground. At 30' in the air my SWR is a bit better that 1.5. Using an analyzer check for resonance/best SWR . If it is above your desired operating frequency lengthen the leads of each side equally. If it is below your desired frequency, shorten each side equally. I'm in the San Francisco Bay Area. This past weekend I made a number of contacts to Anchorage, AK and British Columbia at 100W SSB. Reception on both sides was very good.

 

[cmdrwill]

One thing you might consider is turning your balcony into a ground plane. I don’t know how large it is, but if you could ‘carpet’ it with a wire mesh- like hardware cloth---- mounting the antenna so the base is at the level of this mesh- this is very important-- will give you something approaching a ground plane style antenna. You want to make sure that mesh is all bonded together and it is as close as possible to the base of your multi frequency whip. We are not going for a resonate ground system here, just as good an RF return as possible. The nice thing about a balcony is that you will have an elevated counterpoise- it will minimize the Ground Losses.
* we use hardware cloth for all sorts of RF related things- like that ground plane, or Faraday, static,RF shields- its not just for rodent control anymore…….sorry, (smiles)

Excellent Idea CF.

 

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

To Coyote-Frostbyte. The 2 multi band mobile antennas are already mounted up. Yes going straight horizontal there isn't enough room. So I did an up side down inverted V setup. The coax shield goes to the center connector on the left antenna and the center connector of the coax is connected to the center connector of the right antenna. The ground side of both antennas are connected to gether via pluming pipe that is used for the mount. All bands (80 - 10 meters) get the lowest swr reading on my MFJ-269 analyzer at the bottom of each band (ea: 3.5, 7.0, 14.0, 21.0 and 28.0). I am assuming that I need to make each upper rod just a bit longer to move the lowest swr reading to the middle of each band?

I’m not sure exactly, if this is what you’ll find useful- but first-- as I understand your question, you want some type of couterpoise to work against your balcony mounted multi-frequency antenna…. And you have consider’d using a separate one as this counterpoise, but lack the room to mount it all. You have a good idea, except, as you said- not enuff room for both.
.
One thing you might consider is turning your balcony into a ground plane. I don’t know how large it is, but if you could ‘carpet’ it with a wire mesh- like hardware cloth---- mounting the antenna so the base is at the level of this mesh- this is very important-- will give you something approaching a ground plane style antenna. You want to make sure that mesh is all bonded together and it is as close as possible to the base of your multi frequency whip. We are not going for a resonate ground system here, just as good an RF return as possible. The nice thing about a balcony is that you will have an elevated counterpoise- it will minimize the Ground Losses.
.
As far as the length of the tuning whip?… good question: I know nothing about that particular antenna, though I am sure others here will give you advice. Lacking that, and due to the very short nature of the antenna in terms of degrees of frequency, whatever resonates it would be good with me-- ie: get the lowest SWR.
.
Good luck- hope that planted an idea or two
.
……………………CF

.
.
* we use hardware cloth for all sorts of RF related things- like that ground plane, or Faraday, static,RF shields- its not just for rodent control anymore…….sorry, (smiles)

 

[SCPD]

Hey Steve--

Well, like I said, I am not familiar with the particulars of your antenna- but that being said- if your antenna is achieving its lowest SWR at the bottom of each band- it is resonating there. In order to raise the resonate frequenc(ies) you need to reduce the capacitace in the loading section-- ie: that adjustable whip needs to be shorten'd-- not leghten'd.
.

Now, there may be a problem in doing this as each section for each band has been designed to achieve the lowest SWR with a common whip length. In moving the centre frequency of, say 40 metre's from 7.0 to 7.2 you may able to achieve a good SWR there, but it may mess up, unacceptably, what it does on the other bands.
.
Have fun- antennas can be quite a trip, can't they?
.
.....................CF

 

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

Yes antennas can be quite a trip, I am thinking after I get this antenna setup working 100% or as close as I can to 100% on 80 - 10 meters (The instructions say that this antenna can tune the following bands 7, 6 and 2 meters also). I am only setting it up for 80 -10 meters (it won't do 160 meters). When it is set for the best swr on 80 - 10 meters I am thinking of writing an article, though I don't know were I am going to submit the article.

Hey Steve--

Well, like I said, I am not familiar with the particulars of your antenna- but that being said- if your antenna is achieving its lowest SWR at the bottom of each band- it is resonating there. In order to raise the resonate frequenc(ies) you need to reduce the capacitace in the loading section-- ie: that adjustable whip needs to be shorten'd-- not leghten'd.
.

Now, there may be a problem in doing this as each section for each band has been designed to achieve the lowest SWR with a common whip length. In moving the centre frequency of, say 40 metre's from 7.0 to 7.2 you may able to achieve a good SWR there, but it may mess up, unacceptably, what it does on the other bands.
.
Have fun- antennas can be quite a trip, can't they?
.
.....................CF

 

[steve-kc7byp]

By the way. After I get the swr down to the lowest reading I can with the antenna analyzer on each band. I have a MFJ-901B antenna tuner to refine the antenna tuning with some more.

 

[SCPD]

I think that’s a good idea, Steve, to limit your antennas to HF only….. Not that they wouldn’t work on 6 and 2, but you can devise so many others that will work better. 6 and 2 metre antennas can certainly be “balcony’ suitable antennas, and you seem to be developing a knack as an experimenter..
.
I’ll throw another idea at you- its kind’a novel, and since you like multiband antennas…
.
Find a single band 5/8 wave 2 metre antenna and try it on 6. You will find that its resonator, if adjusted for, say, 147Mhz is really resonating at 49Mhz-- so while the antenna is radiating as a 5/8’s wave, its loading on the 3rd harmonic as a 3/4. Some adjustments may be required, --or not-- to make it dual band… but, hey- in the end you’ll end up dual band, or an either 6 or a 2 metre balcony mounted antenna… and a few points higher up on the antenna experience curve.
.
You mentioned 160.… its just as well it doesn’t cover that band. Does the term “Tesla Coil” evoke any images?…(laffing)...
.. That’s what you’d have if you feed so highly loaded, high Q short antenna like that with any amount of 1800Khz RF. Ever look at a Hustler brand high power 75 meter mobile antenna coil?.. The matching rod has this big aluminum ball at its tip- for good reason!
Here’s one of those reasons:
.
A few years ago I was a consultant on a HIPAS (HIgh Power Auroral Stimulation) project- it was separate but related. We assembled a remote transmitter at a site far out in the bush of Alaska, with a 130Khz 50Kw pulsed transmitter. The antenna was just a fraction of a wave lenght at this frequency, so imagine the Q required and the logistics of the loading system for that antenna. I had a certain (ominous) feeling of what would happen when it went ‘power on‘-- but the results were more than I ever, Ever!- expected. I’ll just say, Nicola Tesla would have been VERY! proud of us!….
..... And we spent the next 2 weeks re-engineering our little project.
.

.
.
…………………….CF

 

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

I have a home made 2m/70m J-pole antenna in the garage. There is only room on the balcony for the one antenna setup. I also have a 2m/70cm magmount mobile antenna sitting on top of outside part of my window air conditioner. Yes I am a big time jarry rigger/experimenter. I live on SSDI and I sometimes have to make due with what is available. I am a retired 2 way radio teck. I have an AA degree in electronics, 2 way radio, tv, vcr and windows based computer repair. I had to retire because I started having micro motor hand shakes, I couldn't hold the soldering iron still anymore. The 1 thing I am not is a designer. I suck at math. I know the electronic formulas and how to use them but with out a calculator I am up a creek with out a paddle, in fact I don't even have the boat. I can barely do simple adding and subtracting with a paper and pencil. I have dyslexia and brain damage from an ABI (acquired brain injury, lack of oxygen) when I was relay young. I still tinker in the hobby when I can. If I had the room to work I would go to the gov surplus auction and buy a pallet of laptops. Fix them up and sell them. Yes I know what a Tesla Coil is. I made one once. I also made a battery operated cw transmitter out of an old car ignition coil. Both of them spladered all over the bands about 2 miles out from the transmit point. No one figured out were the transmit point was because the Tesla Coil and the antenna for the car ignition coil transmitter were hidden in an old wooden shade. I did the Tesla Coil and the cw transmiter back in the days when I was a CB operator before I got my ham license.

I think that’s a good idea, Steve, to limit your antennas to HF only….. Not that they wouldn’t work on 6 and 2, but you can devise so many others that will work better. 6 and 2 metre antennas can certainly be “balcony’ suitable antennas, and you seem to be developing a knack as an experimenter..
.
I’ll throw another idea at you- its kind’a novel, and since you like multiband antennas…
.
Find a single band 5/8 wave 2 metre antenna and try it on 6. You will find that its resonator, if adjusted for, say, 147Mhz is really resonating at 49Mhz-- so while the antenna is radiating as a 5/8’s wave, its loading on the 3rd harmonic as a 3/4. Some adjustments may be required, --or not-- to make it dual band… but, hey- in the end you’ll end up dual band, or an either 6 or a 2 metre balcony mounted antenna… and a few points higher up on the antenna experience curve.
.
You mentioned 160.… its just as well it doesn’t cover that band. Does the term “Tesla Coil” evoke any images?…(laffing)...
.. That’s what you’d have if you feed so highly loaded, high Q short antenna like that with any amount of 1800Khz RF. Ever look at a Hustler brand high power 75 meter mobile antenna coil?.. The matching rod has this big aluminum ball at its tip- for good reason!
Here’s one of those reasons:
.
A few years ago I was a consultant on a HIPAS (HIgh Power Auroral Stimulation) project- it was separate but related. We assembled a remote transmitter at a site far out in the bush of Alaska, with a 130Khz 50Kw pulsed transmitter. The antenna was just a fraction of a wave lenght at this frequency, so imagine the Q required and the logistics of the loading system for that antenna. I had a certain (ominous) feeling of what would happen when it went ‘power on‘-- but the results were more than I ever, Ever!- expected. I’ll just say, Nicola Tesla would have been VERY! proud of us!….
..... And we spent the next 2 weeks re-engineering our little project.
.

.
.
…………………….CF

 

[TheSpaceMann]

I’m not sure exactly, if this is what you’ll find useful- but first-- as I understand your question, you want some type of couterpoise to work against your balcony mounted multi-frequency antenna…. And you have consider’d using a separate one as this counterpoise, but lack the room to mount it all. You have a good idea, except, as you said- not enuff room for both.
.
One thing you might consider is turning your balcony into a ground plane. I don’t know how large it is, but if you could ‘carpet’ it with a wire mesh- like hardware cloth---- mounting the antenna so the base is at the level of this mesh- this is very important-- will give you something approaching a ground plane style antenna. You want to make sure that mesh is all bonded together and it is as close as possible to the base of your multi frequency whip. We are not going for a resonate ground system here, just as good an RF return as possible. The nice thing about a balcony is that you will have an elevated counterpoise- it will minimize the Ground Losses.
.
As far as the length of the tuning whip?… good question: I know nothing about that particular antenna, though I am sure others here will give you advice. Lacking that, and due to the very short nature of the antenna in terms of degrees of frequency, whatever resonates it would be good with me-- ie: get the lowest SWR.
.
Good luck- hope that planted an idea or two
.
……………………CF

.
.
* we use hardware cloth for all sorts of RF related things- like that ground plane, or Faraday, static,RF shields- its not just for rodent control anymore…….sorry, (smiles)

Good point about the mesh! I have actually carpeted a balcony with aluminum foil and had good results! I've even done the same thing indoors on occasion!

 

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

I have the 2nd multi band antenna (the same as the 1st one) in a upward type V mount. The mounting part works great. But the tuning I don't think it is going to work. See the graph that I posted bellow. On a normal antenna graph the swr slowly moves up as you move away (ether side) from the center resonant frequency. On this antenna setup the swr goes up sharp and fast when I move off the center resonant frequency. That I don't know how to fix. The antennas are mounted on a tripod that is held down by 3 cinder blocks and large wire ties. I can't bolt or screw anything to the building or the balcony. If I lay the wire mesh under the tripod, will that work and use just 1 of the multi band antennas? The wire mesh is really cheap.

Good point about the mesh! I have actually carpeted a balcony with aluminum foil and had good results! I've even done the same thing indoors on occasion!

 

[SCPD]

By using a second tuned antenna as a counterpoise, what you have, in essence, is a shorten’d dipole. In simple terms: the shorter it gets, the tighter becomes its tuning requirements as its bandwidth decreases. That adjustable whip is the capacitor that resonates the coil section to the desired frequency-- it becomes a series L/C circuit.
.
Make that coil big enuff and you can, in effect, eliminate that whip. I have seen CB antennas that do exactly that- I think one brand is called a Fire Stick(?)- these antennas are all inductor.
A sort of rule of thumb- the shorter the antenna, the greater the L/C requirements - meaning a higher circuit Q- and a narrower bandwidth.*
.
In this case, by going to a non resonate ground plane, you will not only broaden that bandwidth, but increase the antenna’s efficiency… its not all about just getting a low SWR.
I won’t go into the ‘why’ this is- but I can say with assurance, it was against such a counterpoise the SWR charts for your antenna were generated. If you don’t mind that frequency ‘narrow-ness” and lower efficiency, then the second antenna as a dipole is fine. If not, you will need to address that in some other way--- for you’re going up against two most-powerful forces--- Mother Nature and her Right Hand Girl, ( ) the Law of Physics..... and they don't always play nice.
.
.
……………………..CF

*and for you, the engineers and physicists, I realize this is a vastly over simplification…. So is the Fire Stick analogy.

 

[TheSpaceMann]

I have the 2nd multi band antenna (the same as the 1st one) in a upward type V mount. The mounting part works great. But the tuning I don't think it is going to work. See the graph that I posted bellow. On a normal antenna graph the swr slowly moves up as you move away (ether side) from the center resonant frequency. On this antenna setup the swr goes up sharp and fast when I move off the center resonant frequency. That I don't know how to fix. The antennas are mounted on a tripod that is held down by 3 cinder blocks and large wire ties. I can't bolt or screw anything to the building or the balcony. If I lay the wire mesh under the tripod, will that work and use just 1 of the multi band antennas? The wire mesh is really cheap.

What I have done is to purchase a 2X2 foot piece of sheet metal, and placed it on the floor of the balcony, I then carpeted aluminum foil over the metal, and then over the rest of the balcony floor. Next I attached a heavy duty vehicle magnet mount over the foil right above the metal plate, and screwed my antenna (Hamstick, 9 foot whip, random wire, etc.) into the mount!

 

[steve-kc7byp]

re: a jary riged dipole out of 2 mobile ant's

Update on this post. Probably in Aug, After I get the power steering pump replaced and get my minivan back on the road in July. I am going to buy a MFJ-936B loop tuner and build a weatherproof box for it and mount the weatherproof box on the tripod. And make different size loop antennas for the different HF bands. The loop antenna it self will be on the outside part of the weatherproof box. It means going outside and changing loops and open the door on the box to retune the loop using my MFJ-269 antenna analyzer. This is about the best compromise that I can come up with until my best friend/room mate gets his VA pension and all his back pay. Then we are moving into a house. The place we have in mind has enough room for a half wave 160m loop antenna that will work without a tuner..No restrictions on any antennas because this house will be just outside the city limits in the county. I am looking forward to that day.

Steve