My SWR on 80 meters stinks!

[VE3GZB]

Lou (VE3AWA) loaned me his SWR meter today so I've got it patched into my antenna knifeswitch.

On 80 meters, my reflected power is almost equal to my forward power, guess that explains where my 20 watts is going! Not up the Dipole, that's for sure!

On 40 meters the situation looks better though. Reflected power is roughly half of what Forward power is.

I'm trying to see if loading coils will help me any on 80 meters but I have my doubts so far.

[VE3GZB]

I've been looking up info on random wire tuners and some appear to be just an "L" filter, series-inductor, shunt-capacitor.

So I modified my PI tuner to be an L tuner, easy enough to do. I'm able to get a much improved SWR on the rig now. I can see forward level of "3" and a reflected level less than "1", more like 1/2.

Of course, my frequency counter is going nuts now, it looks like I'm triggering it on a second harmonic or something.

I tried making contacts this evening but I was receiving some SSB conversations from West Virginia, probably out of my range. I'll keep trying with this configuration to see what happens!

I'm sure I'm still running on low power so the upgrade for higher power is still in my mind. But I also have to tackle antenna matching at the same time, otherwise I'd be just dumping high power up the line to be reflected right back down (or something).

I was also looking at this site:

http://www.iw5edi.com/ham-radio/?a-short-dipole-for-80-meters,31

Interesting notion...the parameters might fit my own installation, but I don't have such coils. I have a bunch of other coils, the largest of which measures about 19uH, but it's cumbersome, not the sort of thing to mount up in the air.

73s
geo
VE3GZB

[K1JJ]

Geo,

That 48' dipole with loading coils in the link would be a good choice for your QTH. It wud fit right in and give you a balanced antenna.


You would NOT need an antenna tuner when using it on 75M.  The loading coils help to bring the input impedance up to better match the coax.   It is a one-band antenna when using the coax.

For the loading coils, you could wind some insulated wire on pvc pipe or whatever plastic tubing you have. You wud adjust the amount of turns to give you the best swr at the end of an 84' length of RG-213 coax.  Or, just make them 19uh using an L meter and be done wid it. (Or use an inductance web calculator to estimate the # of turns and diameter for whatever coil form you have)

Give it a try.

If you later build up an antenna tuner (like the K1JJ tuner I posted for you some time back)  you could feed that same antenna with openwire and cover all bands.

BTW, sounds like your old antenna problem was matching. No wonder no one heard you with a near infinite swr. I had assumed you had that L/C network adjusted for best swr.  Or is this with your latest twisted pair feedline?  Either way, an swr under 3:1 is desirable. All newly erected antennas need to be played with to get the right feedline to antenna match. It's part of the installation process.  (with the exception of open wire which uses a tuner for matching)


T

[VE3GZB]

Here's a schematic of my transmitter, I have built-in a Pi tuner but for now I've lifted the connection to the plate tuning cap so the Pi tuner becomes an "L" tuner. SWR looks better now than when I ran it as a Pi tuner.

I'm not sure if I'm putting any signal out....I wanted to try it this morning (Sunday) on the DX60 net but conditions were sure noisy, also they just kept talking, talking, talking, not giving anyone else a chance to "break in". 

I'm not sure what gauge wire I should use. Loading seems to be a good idea, but of course I'm worried that loading would cripple my antenna's bandwidth.

But the only wire I have in abundance is a 10,000 ft spool of insulated 26 ga. my boss gave me. (I have scraps of other wire but nothing in any decent quantity).

I think number 26 wire might be too light for antenna loading coils, especially if I want to go higher power. BTW, if anybody needs a few hundred feet of number 26, just e-mail or PM me and I can give you some ! I'd never use 10,000 feet in my entire life!

Oh, I'm not running any Coax - I never did, it's too expensive!!! 

Originally I tried running a Zepp and fed it with 450 Ohm twinlead I got cheap at a hamfest. Then others convinced me that a dipole was the answer, so my boss gave me a few hundred feet of number 16, which I paired up, twisted up in a drill and taped up to give me a transmission line (I have a very good boss, he gives me his surplus stuff for free).

If a loaded dipole isn't the answer, then I'll just have to pull it down and reuse the materials to some other configuration.

[KD6VXI]

Originally I tried running a Zepp and fed it with 450 Ohm twinlead I got cheap at a hamfest. Then others convinced me that a dipole was the answer, so my boss gave me a few hundred feet of number 16, which I paired up, twisted up in a drill and taped up to give me a transmission line (I have a very good boss, he gives me his surplus stuff for free).

If a loaded dipole isn't the answer, then I'll just have to pull it down and reuse the materials to some other configuration.

Try spacing your transmission line about 4 to 6 inches apart, rather than twisted pair.

Twisted pair was NEVER good at RF frequencies we use.

It's good for keeping things balanced at 60 hertz, though...  And it keeps things sheilded at audio freq.s (to an extent)...

BUT, you want parallel lines, not twisted, to be your transmission line.

And the SWR meter your looking at is probably "calibrated" against a 50 ohm load (diffferent meter config's operate differently.  If it's a simple voltmeter, then you're probably OK).

An Ammeter would be better, two really... One for each side of the feeder.

Google balanced feeders and see what you can come up with on that side.

Twisted Pair is good for networking.. . Not Radio!

--Shane

[VE3GZB]

Try spacing your transmission line about 4 to 6 inches apart, rather than twisted pair.

Twisted pair was NEVER good at RF frequencies we use.

It's good for keeping things balanced at 60 hertz, though...  And it keeps things sheilded at audio freq.s (to an extent)...

BUT, you want parallel lines, not twisted, to be your transmission line.

And the SWR meter your looking at is probably "calibrated" against a 50 ohm load (diffferent meter config's operate differently.  If it's a simple voltmeter, then you're probably OK).

An Ammeter would be better, two really... One for each side of the feeder.

Google balanced feeders and see what you can come up with on that side.

Twisted Pair is good for networking.. . Not Radio!

--Shane

No can do....my wife already doesn't like me suspending twisted pair in the back yard, she won't hear of me turning the yard into a lab experiment. She supports me being interested and building stuff but she won't hear of me turning the house or the yard into a radio lab.

All I have is this twisted pair (which historically has been used by Hams in the 20s and 30s, so I've read) or what's left of my 450 Ohm twinlead.

Since dismantling the Zepp, the twinlead is not in one long piece anymore, no way I could remove it from the wall, I tried tugging at it hard and it won't budge, it's in there for good. So I simply cut and left about 6 inches of the twinlead in the wall on either side and then spliced/soldered/insulated my twisted pair to this. It's my only choice really.

[VE3GZB]

Well I modified my 45 foot long dipole now, I put loading coils in the middle of each leg of the dipole.

I used two old plastic spools from solder as my coil forms and I scrounged around and dug up a bunch of unused 16 ga. stranded speaker wire. I wound each coil to about 74uH (used my L/C meter), taped them up and put them in place.

Luckily I had two dogbone insulators left! I'll give it a try and see what things look like!

73s
geo
VE3GZB

[KD6VXI]

Well I modified my 45 foot long dipole now, I put loading coils in the middle of each leg of the dipole.

I used two old plastic spools from solder as my coil forms and I scrounged around and dug up a bunch of unused 16 ga. stranded speaker wire. I wound each coil to about 74uH (used my L/C meter), taped them up and put them in place.

Luckily I had two dogbone insulators left! I'll give it a try and see what things look like!

73s
geo
VE3GZB

Do all you want on the antenna end, your feedline is your biggest problem, as well as your measuring equipment.

--Shane

[VE3GZB]

You're probably right....it's an imperfect solution in an imperfect world. I'll just try my best with what I have on hand.

So far the SWR looks much better, I can say that much. But it's too noisy now, been noisy all morning in my area, so I'll try later in the evening to see if I can raise any contacts.

If my SWR looks better and actually IS better, then when I build again to raise power, at least I may be able to put more of that power to the antenna.

[WA1GFZ]

KB3AHE ...time to show this guy a better way

[The Slab Bacon]

KB3AHE ...time to show this guy a better way

Frank,
         I posted it in an earlier thread, but here it is again.

with a descent tuna it will work anywhere from 160-10 as long as long as you do everything you can to minimize the I-R losses!!

I know it works, many have heard me on 160, 75 and 40 with it. I am space challenged here as well, but it takes much more than that to keep me off of the air!

sometimes yo just gotta do what ya gotta do.! (Obscene power never hurts either) 

                                                          The Slab Bacon

[W1GFH]

Google balanced feeders and see what you can come up with on that side.

No can do....my wife already doesn't like me suspending twisted pair in the back yard, she won't hear of me turning the yard into a lab experiment. She supports me being interested and building stuff but she won't hear of me turning the house or the yard into a radio lab.

That brown "windowed" ladder line DOES seem to visually stand out on a home. For a cheap and very functional "stealth" balanced line, I've found that Radio Shack 300 ohm TV Twinlead (still available at RS over the counter) combined with an antenna made from #18 black insulated, stranded wire plus some fishing line is virtually INVISIBLE to wives and neighbors alike. There's something about TV twinlead that makes it blend in with the surroundings and look so harmless and "normal" most people fail to even notice it.

[K1JJ]

It's funny what is noticed and what is not.

Back in the mid 90's the AM mobile craze was hot and we were all putting the biggest antennas we could on our vehicles.

Towards the peak I had an elaborate 75M bugcatcher style antenna that had a large spoked capacity hat, a huge broadcash coil and an 18' whip that extended over the complete Blazer.  I would constantly get looks of disbelief on the highway.

Dino/WA1KNX was even more radical. In the back of his pickup truck he had a 5 gallon plasdick pail with copper tubing wound on it and a set of 2X4's holding up this monster whip. It was an eyesore.  But ya know what? Nobody gave his truck a second glance. It just looked like a construction worker with his truck all loaded up with junk. I rode behind him once and saw for myself - nobody cared.

We went on to think that a great capacity hat would be a large insulated ladder on top of the roof of the truck laying horizontally as normal. Again, nobody would give it a second look cuz it's the norm.

Bottom line is you can drive a Mack truck that stands out like a tank and nobody notices, but drive a pink candy cane PT Cruiser and they stare. 

The TV twin lead is a perfect example as to what the public is used to seeing (at least in the past on TV antennas) and is psychologically invisible..

T

[KB2WIG]

Ham radio is a hobby.

I was first interested in 'it' when I heard Norm, k2klv, (king 2 king loves victor)  overload my transistor (radio).  This was around my 8th birthday. I was finally licensed ~30 years later. I consider myself a ham; it's what I Am.

My wife was aware of my hamishness before we married.  I 'put up' with her, she can 'put up' with me, my antenna and my radios. 

Good luck with your antenna work.

KLC

p.s. Check out my 10m dipole pictured in the Gallery. My wife uses it all the time.

[ka3zlr]

Ya Know I'll be Honest guys.....I never liked more than one antenna on any of my trucks....I see some of these killer VHF'rs rides Man......antenna Farms...

73
Jack.

[VE3GZB]

KB2WIG: You're using a clothesline as the antenna? With the clothes hanging on it? Doesn't that cause problems?

My antenna is longer than our clothesline but I'm using up all of the mountable space I can. There are many tall trees on the neighbour's property as there are all over, I'm sure they're not good as RF reflectors.

The Slab Bacon: What does the non-connected line do in your antenna design? The remainder looks just like my dipole did, but I have only 45 feet to work in, your design is 60 feet long. Are you using the non-connected line as a reflector?? How would that work, it seems too close to be a reflector?

I've been trying to research things and this is what I'd found so far.

On my antenna I put the loading coils in, just like it's illustrated here:

http://www.qsl.net/qrp/ant/short80.htm

My SWR is improved, it's no longer at infinity, forward energy is about double of the reflected energy according to the SWR meter. I'm still probably not pushing enough power out though.

In the example shown, the antenna is 48 feet long. Mine is max. 45 feet, so I put a few more turns on the loading coils, they're about 74 uH each as opposed to 67 uH.

The characteristic impedance of a twisted pair is not too far off from the resonant impedance of a dipole (theoretically around 73 Ohms). Cat 5 cables are nothing but twisted pair, their characteristic impedance is about 100 Ohms, they work well and prove that twisted pair are a reliable technology for high frequency work (Cat 5 works up to 100 Mhz).

http://en.wikipedia.org/wiki/Category_5_cable#Category_5

Twisted lamp cord, etc....not too far from that either and according to any number of old Ham literature I've gotten and read (old QSTs from the 20s and 30s, reprinted radio material available from Lindsay publications), using lamp cord or twisted pair as a transmission line was not uncommon.

The SWR from such a small mismatch isn't very high. If I were to use my 450 Ohm twinlead instead, the mismatch between 450 Ohm to 73 Ohms would be much more serious.

If I run the Agilent simulator (below), let the TX and line remain at 50 Ohms and my load at 500 Ohms, my VSWR is 10:1. Now 450 isn't too far from 500 and 73 isn't too far from 50, so these numbers would still tell me that using 450 Ohm line (or perhaps even 300 Ohm line) to match 73 Ohms just don't sound right.

Granted, it'd be nice to be dead on, but that's just not going to happen on a realistic budget.

I found this from Agilent, it's a java thing to simulate impedance matching/mismatching:

http://education.tm.agilent.com/index.cgi?CONTENT_ID=6

The real solution that would, I think, correctly address the root problem is to 1) have more property so I can put up a longer dipole, or 2) to construct my transmitter to work at much higher frequencies than 3-4 Mhz.

More property is out of the question - property here is crazy expensive - so I might end up rebuilding to try to work AM on 20 meters. At that frequency my dipole would be a closer fit than at 80 meters and I could remove the loading coils.

Of course then I'm left wondering...who works AM on 20 meters?

40 meters might work ok, so perhaps doing my transmitter to be able to switch from 40 to 20 meters would be a soltuion.

Or does anyone have any formula to fit a pure unloaded 80 meter antenna into a 45 foot long distance?

Thanks,
73
geo
VE3GZB

[KF1Z]

The Slab Bacon: What does the non-connected line do in your antenna design? The remainder looks just like my dipole did, but I have only 45 feet to work in, your design is 60 feet long. Are you using the non-connected line as a reflector?? How would that work, it seems too close to be a reflector?

Don't see any part that is "non-connected"......

It's a folded dipole, that is open at the top....




Put up Slab's antenna, as an inverted V.

Use open line, or any of the other suggestions...


When your wife starts to say something about it..  ask her what patern wallpaper she'd like installed in the living room.

give and take.

[VE3GZB]

She hates wallpaper and it took her a long time to make the backyard look nice. You don't know my wife's temper.

[KB2WIG]

  " KB2WIG: You're using a clothesline as the antenna? With the clothes hanging on it? Doesn't that cause problems?   "

There's no problem as long as I don't say anything to the wife.


klc

[N3DRB The Derb]

My wife comes to hamfests with me, rolls the goodie cart around while I fill it, gives me money to buy things, and supports my ham radio 120%.  She cares not about any antenna I put up. She thinks ham radio is saving my life (I tend to agree).

In return, she goes to as many dog & cat, bead, and homemade jewelry shows she wants. It's called give and take and being supportive of what makes your mate happy.

Thats why my girl is RED HOT!   

Geo, you'll never get out unless you get your antenna deal negotiated out with yer wife. Maybe 40 meters would be more doable for you. 75 meters is tough enough with low power and a full sized dipole.

can you post some pix of yer house so we can see how things are arranged? I have a feeling 2 or 3 pictures would be worth 5000 words.

[AF9J]

Hi Geo,

I wasn't going to chime in, but (and I know it's already been talked about) that twisted pair feedline gives me bad vibes.  Yeah, I know, in the 20s & 30s there were hams who used a twisted pair for a feedline, but back then, antenna knowledge was still very incomplete, so, they used what they had not knowing about its limitations.  Besides impedance issues, one of the biggest reasons twisted pairs are not a good choice to use, is because they are lossy at RF frequencies. 

http://www.eham.net/forums/QRP/3462

I agree with whaot was said by others - may get some cheap 300 ohm TV twin lead.

Also, another thought that comes to mind, is the Pi-Network (now being run as an L-network) in your transmitter.  Since you're dealing with some pretty heavy duty impedances, it may not be up the the impedance matching requirements your antenna requires (this is a pretty common situation with built-in Pi-networks, that'll typically match say from 10 ohms to about 2000 ohms impedance - not the uber low [below 10 ohms] impedance you may be dealing with ).

Just Some Thoughts,
Ellen - AF9J

[K1DEU]

   If you have a balanced line ATU (antenna tuner unit) Don't forget one of my favorite options to use two Coax Lines. Join the braids beginning and end and ground the braid at ATU to Earth. I like two runs of RG-11 A/U or LMR400. Someone should manufacture a nice center insulator with two type "N' Females. No questions remain about our feedline radiating, being buried (use buryflex) picking up unwanted stuff or taping to metal masts or towers ! 73  John, K1DEU

[The Slab Bacon]

Geo,
       there is no part of my antenna that is not connected. It is simply a folded dipole that does NOT make a complete loop. It is open at the top where the top dogbone insulator is.

Some have also called it a "linear loaded dipole". I just call it my antenna. It is a very old design from an old "west coast handbook". It is supposed to use tuned feeders, but I didnt have enough room for them, so I used what I could and let the tuna do the rest of the work. If you work hard to control the I-R losses, it will put out a respectable signal even at lower power levels. A good strapping low-loss tuna is the real secret to making it work.

Karl, (KD3CN) put up a stretched one as an inverted V and does very well with it as well.  I know it works as no one ever seems to have any trouble hearing me.

I also agree with some of the others, it sounds like it is time for some political negotiations with "the war dept."

                                                                  the Slab Bacon

[flintstone mop]

George,
If you're trying to resonate a 50ohm system then the MFJ 259 would be a better tool. At least you will be able to figure out what is killing the system. Too much inductance or capacitance.
Open ladder-line and the famous K1JJ tuna answers all of these challenges.

And Tom Vu As long as Dean wasn't using that big plasdick pail for the ground rod it was ok.
CBers would carry dirt around in the trunk or a construction bucket with salt water and sand to get their ground connection. camawn

Fred