Radio Preppers

General Category => Antennas => Topic started by: Geek on July 01, 2013, 08:18:17 AM

Title: 2m antenna tuning
Post by: Geek on July 01, 2013, 08:18:17 AM
I've been able to communicate okay on my 2m radio, but in trying to get email to work over the local packet network we've traced the problem to the antenna.  I do not have an antenna tuner, which seems to be one alternative and have read recommendations to trim the antenna based on SWR measurements, which strikes me as a quick way to ruin a perfectly good antenna.  When looking for tuners I seem to find plenty of HF alternatives, but not much for 2m.

What do those of you who use 2m do?
Title: Re: 2m antenna tuning
Post by: KK0G on July 01, 2013, 08:49:22 AM
First of all I'd forget about a 2 meter tuner, they're not only completely unnecessary but also counter productive. At VHF frequencies the loss in the coax from an SWR high enough to require a tuner would be horrendous. I wouldn't worry about ruining your antenna by trimming it, that's how it's done. Just take your time, pay close attention to what you're doing and you'll be fine.

Are you sure the problem is in the antenna? It seems very odd that it works fine on phone but not packet. 2 meter antennas are usually broad banded enough to easily cover the entire band with no problems, hell many times I've used business band antennas for use around 154 MHz on 2 meters without adjusting them at all.
Title: Re: 2m antenna tuning
Post by: Geek on July 01, 2013, 09:12:18 AM
Quote from: KK0G on July 01, 2013, 08:49:22 AM
First of all I'd forget about a 2 meter tuner, they're not only completely unnecessary but also counter productive. At VHF frequencies the loss in the coax from an SWR high enough to require a tuner would be horrendous. I wouldn't worry about ruining your antenna by trimming it, that's how it's done. Just take your time, pay close attention to what you're doing and you'll be fine.

Are you sure the problem is in the antenna? It seems very odd that it works fine on phone but not packet. 2 meter antennas are usually broad banded enough to easily cover the entire band with no problems, hell many times I've used business band antennas for use around 154 MHz on 2 meters without adjusting them at all.

At the moment the antenna is the only thing that we haven't gone over multiple times.  The indicators on the TNC and the radio indicate transmission is occurring, but receiving seems to be sporadic.
Title: Re: 2m antenna tuning
Post by: KK0G on July 01, 2013, 10:37:51 AM
I'm far from a packet expert but I did mess with it a little bit many years ago. I do remember that it requires a good strong signal in order to reliably decode, more so than phone. How strong of a signal are you receiving? What's the antenna? How high is the antenna? Is it fed with good low loss feedline?
Title: Re: 2m antenna tuning
Post by: Geek on July 01, 2013, 12:32:35 PM
Quote from: KK0G on July 01, 2013, 10:37:51 AM
I'm far from a packet expert but I did mess with it a little bit many years ago. I do remember that it requires a good strong signal in order to reliably decode, more so than phone. How strong of a signal are you receiving? What's the antenna? How high is the antenna? Is it fed with good low loss feedline?

I've used a couple different antennas.  All the equipment is on the second floor of the house in a room with very large windows facing in the right direction.  I am on the side of a hill and the ground drops away in that direction.  The only feed lines are the cables that came incorporated into the antennas.  Everything is right together.
Title: Re: 2m antenna tuning
Post by: KK0G on July 01, 2013, 01:00:58 PM
Quote from: Geek on July 01, 2013, 12:32:35 PM
Quote from: KK0G on July 01, 2013, 10:37:51 AM
I'm far from a packet expert but I did mess with it a little bit many years ago. I do remember that it requires a good strong signal in order to reliably decode, more so than phone. How strong of a signal are you receiving? What's the antenna? How high is the antenna? Is it fed with good low loss feedline?

I've used a couple different antennas.  All the equipment is on the second floor of the house in a room with very large windows facing in the right direction.  I am on the side of a hill and the ground drops away in that direction.  The only feed lines are the cables that came incorporated into the antennas.  Everything is right together.

I'm assuming this is an indoor antenna, what kind is it? Can you try an outside antenna mounted high in the clear?
Title: Re: 2m antenna tuning
Post by: Geek on July 01, 2013, 02:17:16 PM
The antenna is a wire hanging in the window facing in the direction of where the packet site is.  Putting an outside antenna on the roof is an option, the attic would get me a few feet higher, and a better quality antenna could be purchased.  I would prefer to stay inside as anything outside would be vulnerable to the next Hurricane Sandy, which is exactly when I want to be able to use this capability.  In addition, I am not a young guy and I am disinclined toward going up on the rather high roof.  I would need to hire someone to get the thing up there.

The window the wire is in is at least 25' above ground level now and the ground drops away in the required direction.

I have also tried a Larsen mobile antenna, but that didn't work too well without a large metal ground plane.  I intend to try that again with a decent ground plane, but have no assurance of a better result until I try it.  I'm really looking for additional ideas of things I can do without the hassle of getting on the roof.
Title: Re: 2m antenna tuning
Post by: KK0G on July 01, 2013, 03:16:05 PM
Remember the old adage; "A crappy antenna up high beats a great antenna down low". Of course that's generalizing and ignoring lots of possible variables but it holds a lot of truth. Ditto outdoor vs. indoor antennas. This is one of those situations where it's very difficult to visualize and diagnose remotely, If we were neighbors I'd just come give you a hand but alas............ Is there a ham club, Elmer, or ham experienced with VHF and or packet experience near you that could take a look at your set up?
Title: Re: 2m antenna tuning
Post by: gil on July 01, 2013, 04:02:06 PM
It might be that the antenna is too close to, well, anything, especially any metal. For a directional transmision, given the small size of 2m antennas, I'd try a Yagi or a quad, even a Moxon, which would be the simplest...

Gil.
Title: Re: 2m antenna tuning
Post by: KK0G on July 01, 2013, 04:15:41 PM
Quote from: gil on July 01, 2013, 04:02:06 PM
It might be that the antenna is too close to, well, anything, especially any metal. For a directional transmision, given the small size of 2m antennas, I'd try a Yagi or a quad, even a Moxon, which would be the simplest...

Gil.

Good idea Gil. It wouldn't take much at all to slap together a 3 or 4 element Yagi, especially for 2 meters, they can literally be built from a broom handle and coat hangers.
Title: Re: 2m antenna tuning
Post by: gil on July 01, 2013, 04:18:04 PM
Yep, the Moxon is even easier! Or, see the Slim Jim I built in the antennas board, though that isn't directional...

Gil.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 01, 2013, 04:47:10 PM
Quote from: Geek on July 01, 2013, 08:18:17 AM
  When looking for tuners I seem to find plenty of HF alternatives, but not much for 2m.

What do those of you who use 2m do?

I agree with those here who have said that an antenna tuner for VHF and/or UHF is a step in the wrong direction.    The reason they are so plentiful on HF is because on some of the designs of 40 meter antennas (as an example) are such that a tuner is required, due to the balun inside.  Plus, if you take my 270' long wire as an example, you have to 'tune' the system any time you change frequencies.

But on VHF, the first step should be to determine what the SWR is.  I think (but I can't be sure) that the radio that Dave let you borrow has an SWR meter incorporated into it.  By keying the mike and setting the meter appropriately, you should be able to determine if you're getting a huge amount of power blasted back at you -- a bad thing.  The SWR in that case would be very high and the meter would show that. 

That situation you can fix.  Tell Dave what your findings are (SWR-wise) and that will tell him that there's something very wrong with either the antenna connectors, the coax, or the antenna itself -- usually a simple thing to rectify.

Best 73

Luck, WA4STO

(http://www.hurderconsulting.net/radiostuff/cqtube.giv)
Title: Re: 2m antenna tuning
Post by: Quietguy on July 01, 2013, 05:08:41 PM
Quote from: KK0G on July 01, 2013, 10:37:51 AMI do remember that it requires a good strong signal in order to reliably decode, more so than phone.

I ran into this not long ago trying to do 2 meter WL2K via a digipeater - some days it worked and some days it didn't.  I thought it was the WL2K station being up and down until I tried some peer to peer via the same digipeater with a friend who lives beyond simplex distance from me.  The bottom line is my connection to the digipeater station is marginal and sometimes it works - other times it works poorly or not at all.

One problem with packet is it is hard to judge the quality of the signal by listening to it because packet bursts inherently sound like they have static noise mixed in.  You really need a full quieting signal; any noise mixed in will degrade the connection.

What kind of wire antenna do you have - is it a commercial unit or did you build it yourself? 

Wally
Title: Re: 2m antenna tuning
Post by: Geek on July 02, 2013, 01:05:08 AM
Quote from: WA4STO on July 01, 2013, 04:47:10 PM
Quote from: Geek on July 01, 2013, 08:18:17 AM
  When looking for tuners I seem to find plenty of HF alternatives, but not much for 2m.

What do those of you who use 2m do?

I agree with those here who have said that an antenna tuner for VHF and/or UHF is a step in the wrong direction.    The reason they are so plentiful on HF is because on some of the designs of 40 meter antennas (as an example) are such that a tuner is required, due to the balun inside.  Plus, if you take my 270' long wire as an example, you have to 'tune' the system any time you change frequencies.

But on VHF, the first step should be to determine what the SWR is.  I think (but I can't be sure) that the radio that Dave let you borrow has an SWR meter incorporated into it.  By keying the mike and setting the meter appropriately, you should be able to determine if you're getting a huge amount of power blasted back at you -- a bad thing.  The SWR in that case would be very high and the meter would show that. 

That situation you can fix.  Tell Dave what your findings are (SWR-wise) and that will tell him that there's something very wrong with either the antenna connectors, the coax, or the antenna itself -- usually a simple thing to rectify.

Best 73

Luck, WA4STO

(http://www.hurderconsulting.net/radiostuff/cqtube.giv)
I believe the HF radio he has offered has that capability.  The 2m he provided for testing is more powerful than mine, but doesn't have an SWR.  I'm going to get a meter from either Dave or some other source to check the SWR on each of the antennas.  The plan has been to get this working before spending much time on HF issues.  He's given me several ideas but I figured I'd collect alternatives as well.

Among the ideas are testing from inside the attic and mounting a pretty serious roof mount antenna, though with the height of my roof, that is beyond anything I want to attempt myself.

From the way the conversation with Dave has gone and the suggestions here, it seems the first thing to do is get an SWR meter and see how much of an issue I have with the existing antennas.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 02, 2013, 07:58:06 AM
what bugs me the most about your difficulty is something that likely bothers you a LOT more -  :(

And that's the idea that you can do ok on 2 meter voice, just not on packet. 

KK0G correctly points out that decoding  blurrrrrrrrrrrrrrps of packet is somewhat more iffy than voice.

My guess is you'll find that the SWR is within reason and that there's some tweaking of the antenna itself necessary to ensure the very best signal possible.

One day soon, you'll find that these difficulties are behind you and then you'll move on to WINMOR/WINLINK and NTS(D) PACTOR, each of which will give you national capability.  Still, I remember when I was first doing packet (on Cape Cod) -- what a marvelous thing to experience.  It really was slick.

73

LH
Title: Re: 2m antenna tuning
Post by: Geek on July 02, 2013, 08:09:53 AM
Well, I'll be a lot less bothered when the problem is solved.  My dilemna is that the solution that Dave and I are sure would work, i.e. a really good antenna on top of the roof, is one I can't implemement without getting some help, would not hold up in the next Hurricane Sandy, and I would not be able to repair it myself.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 02, 2013, 09:51:22 AM
Quote from: Geek on July 02, 2013, 08:09:53 AM
can't implemement without getting some help, would not hold up in the next Hurricane Sandy, and I would not be able to repair it myself.

I understand.  And I share the same situations in that:

1.  I couldn't deal with my roof antennas myself.   So, when I had a contractor in to do some other work (installing the wood stove, eight foot grounding rods in the shack, etc) I had him go up on the ladder and put up the 12 element beam and rotor for 2 meters.  Now I can get to the fifty - mile - away repeater just fine.

2. Here in the Midwest, we have tornadoes.  Nothing like Sandy, that's for sure, but if the roof antennas suddenly went away, it wouldn't bother me in the least, since my nationwide prepper comms efforts are almost always on 40 meters and that's just a wire.  All I have to do is throw a hammer up in a branch and I'm back on the air.

I realize that when you're starting out, it seems that there's always something that gets in the way of success.  Still, I've found that my prepping "mentality" works best for me when I plan for more than one method.  So, for me, it was vhf AND hf.  When I had trouble with one, I fell back to "plan B" until I could get help with Plan A.  Eventually, it all comes to fruition.

73

Luck, WA4STO
Title: Re: 2m antenna tuning
Post by: Geek on July 02, 2013, 02:54:46 PM
Sounds like a healthy attitude.  Considering that 6 months ago I didn't have a HAM license and now I have a General license and a couple radios, I am progressing well enough.  I expected I'd hit some challenges.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 02, 2013, 03:28:33 PM
Quote from: Geek on July 02, 2013, 02:54:46 PM
Considering that 6 months ago I didn't have a HAM license and now I have a General license and a couple radios, I am progressing well enough.

Talk about a healthy attitude! 

You can be sure that a bunch of us here (and elsewhere) enjoy watching your progress. 

73

Luck
Title: Re: 2m antenna tuning
Post by: Geek on July 02, 2013, 08:24:21 PM
Thanks.  I am also still progressing on other things besides communications, e.g. the old Suburban that is now in the restoration shop, slowly adding to consumables, etc.  Yesterday I was explaining to the shop owner that I was going to want to mount a couple antennas in the truck while it was apart.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 02, 2013, 08:38:56 PM
Actually, that's another possibility...

...  back when I was working, I was consulting all around the country.  My last gig was for the Governor's office in Des Moines.  There was rarely a way to put up effective antennas at hotels, campgrounds, etc, so what I often did was run the coax out to the car.

You could do the same, although it wouldn't be anywhere near as effective as a decent antenna at height.  But you could run the coax from the car in to the radio shack and still do better than an inside antenna.

Also, it would be a way to compare the house antenna to a "known" antenna (the one on the car).

Glad I'm retired!

73

Luck

(http://www.hurderconsulting.net/radiostuff/smallcall.jpg)
Title: Re: 2m antenna tuning
Post by: Geek on July 03, 2013, 08:33:33 AM
Using a car is one test I may run, but I am most hopeful that I will succeed in the attic, either with an existing antenna, or with a better antenna.  Since the house is pretty high, on the second floor of the house I am already 20+ feet higher than the roof of a car.  The attic will be another 8' higher, albeit with the roof interfering, and finally I could go with a better antenna inside the attic.  Outside on the roof has all the disadvantages I mentioned earlier.

After this dialog and talking to Dave, I've decided not to go for a roof antenna for VHF, even if it means failure on packet radio.  If that happens I am going to turn my attention to HF, where I can string a wire in the trees without getting on the roof.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 06, 2013, 06:23:10 PM
Quote from: Geek on July 03, 2013, 08:33:33 AM

After this dialog and talking to Dave, I've decided not to go for a roof antenna for VHF, even if it means failure on packet radio.  If that happens I am going to turn my attention to HF, where I can string a wire in the trees without getting on the roof.

I heard from Dave just a bit ago and apparently he's now suggesting that the one 2 meter antenna was of poor design, or construction but that you've got a mag-mount that checks out just fine. 

I continue to be optimistic that you're in such a fabulous place for vhf activity that even a minimal antenna should do the trick.

I applaud your idea of doing what you can on vhf first and if that fails temporarily, concentrate then on a wire for HF operations.

I put an antenna (an expensive 9 band vertical) up on Craigslist last night and it wasn't there but half an hour before it sold.  And I live out in the boonies of Nebraska.  So now I have enough cash on hand, according to the wife, that I can buy a whopper of an HF amplifier.  But Dave has been (correctly) reminding me that I could be much more value to the digital infrastructure if I'd spring for a high speed modem, which would be half the price of the amplifier, and which would make the wife's smile that much larger (always a good thing). 

Ah, decisions, decisions...

73

Luck, WA4STO
Title: Re: 2m antenna tuning
Post by: gil on July 06, 2013, 07:01:58 PM
QuoteI can string a wire in the trees without getting on the roof.

For 2m you could make a ladder-line Slim-Jim antenna and hoist that in a tree...
Very easy/cheap, and discreet..

Gil.
Title: Re: 2m antenna tuning
Post by: Quietguy on July 06, 2013, 09:50:03 PM
Quote from: WA4STO on July 06, 2013, 06:23:10 PMI could be much more value to the digital infrastructure if I'd spring for a high speed modem

If you are talking about an SCS modem... if you haven't seen Pactor 3 in action, I think you would be amazed at its performance compared to other modes.  I have the older SCS PTC-IIex and it still amazes me when I connect to another station that is buried in the noise.

I don't know what your plans would be for a high power amp, but I would buy two SCS modems (one for backup) before I would spring for an expensive HF amp - but I don't do HF amp kind of things.

Wally
Title: Re: 2m antenna tuning
Post by: WA4STO on July 06, 2013, 11:15:08 PM
Quote from: Quietguy on July 06, 2013, 09:50:03 PM


If you are talking about an SCS modem...

Yes, that's exactly what I was referring to.  NTS(D)'s Pactor systems use them for anything faster than P-1 and, although I never have enough traffic to really need anything faster ... well ... sure would be nice to be able to do P-3.  Yumm...

73

LH
Title: Re: 2m antenna tuning
Post by: Geek on July 07, 2013, 11:29:12 AM
Quote from: WA4STO on July 06, 2013, 06:23:10 PM
Quote from: Geek on July 03, 2013, 08:33:33 AM

After this dialog and talking to Dave, I've decided not to go for a roof antenna for VHF, even if it means failure on packet radio.  If that happens I am going to turn my attention to HF, where I can string a wire in the trees without getting on the roof.

I heard from Dave just a bit ago and apparently he's now suggesting that the one 2 meter antenna was of poor design, or construction but that you've got a mag-mount that checks out just fine. 

I continue to be optimistic that you're in such a fabulous place for vhf activity that even a minimal antenna should do the trick.

I applaud your idea of doing what you can on vhf first and if that fails temporarily, concentrate then on a wire for HF operations.

I put an antenna (an expensive 9 band vertical) up on Craigslist last night and it wasn't there but half an hour before it sold.  And I live out in the boonies of Nebraska.  So now I have enough cash on hand, according to the wife, that I can buy a whopper of an HF amplifier.  But Dave has been (correctly) reminding me that I could be much more value to the digital infrastructure if I'd spring for a high speed modem, which would be half the price of the amplifier, and which would make the wife's smile that much larger (always a good thing). 

Ah, decisions, decisions...

73

Luck, WA4STO
Dave tested both antennas.  One is garbage and the other is a decent mobile antenna.  If I can get the mobile to work that would be wonderful. but I am not really expecting it to handle the Packet network.  He has recommended a Comet GP-3 as the next step in antennas.  While he has been recommending putting it on the roof I think he has finally figured out I am not real keen on that idea and I intend to test in the attic first.  We have a major local Hamfest coming up, so I am going to shop for the antenna there.

If I still can't get the packet network to function even with the GP-3, then I am going to drop that approach and move on to HF.

Meanwhile I am debating with myself about antennas for the Suburban project.  I need to figure out what antennas, where to mount them, how to mount them, how to mount the radios and how to route all the resulting cables.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 07, 2013, 12:04:47 PM
Quote from: Geek on July 07, 2013, 11:29:12 AM
Meanwhile I am debating with myself about antennas for the Suburban project.  I need to figure out what antennas, where to mount them, how to mount them, how to mount the radios and how to route all the resulting cables.

Are you considering VHF or HF for the Suburban?  Or both? 

At the risk of making it seem overly complicated, be sure to wade through K0BG's site, particularly with regard to proper grounding of mobile antennas.  http://www.k0bg.com/ (http://www.k0bg.com/)

73

LH
Title: Re: 2m antenna tuning
Post by: Geek on July 07, 2013, 07:39:44 PM
Quote from: WA4STO on July 07, 2013, 12:04:47 PM
Quote from: Geek on July 07, 2013, 11:29:12 AM
Meanwhile I am debating with myself about antennas for the Suburban project.  I need to figure out what antennas, where to mount them, how to mount them, how to mount the radios and how to route all the resulting cables.

Are you considering VHF or HF for the Suburban?  Or both? 

At the risk of making it seem overly complicated, be sure to wade through K0BG's site, particularly with regard to proper grounding of mobile antennas.  http://www.k0bg.com/ (http://www.k0bg.com/)

73

LH
For something actually wired into the vehicle, VHF.  Anything HF would be in a box to be used when pulled over.  :-)
Title: Re: 2m antenna tuning
Post by: WA4STO on July 14, 2013, 04:40:41 PM
Geek - I hear that congrats are in order; you are successfully connecting to WA2IMS now!

I remember, when I lived in CT that the WA2SNA node was very capable.  That is, it had a HUGE number of other stations available to connect to through it; it was very popular.

Course, that was decades before guys like WB2FTX had NTS(D) pactor nodes and MBOs up and running.  These days, even with far fewer people using VHF packet, there's still a ton of fun (and utility) to be had.

I've had some recent successes of sorts as well in the past couple of weeks.

1.  Got a message from a guy in Kentucky who had delivered one of my radiograms there locally.  He really wanted to know how to do much more traffic handling on the digital modes, so I got him set up (he did all the work; I just gave him advice) on WINMOR/WL2K.  That didn't take any time at all and when he was done, I had the 9th region pactor (in Indiana) hub start forwarding traffic for his area code down to him in KY.  Which is great because, until now, we didn't have any outlets for that area code and now we have at least one.

2.  I had suggested to a traffic-handling friend in MN, who seriously loves Morse, to consider becoming the recipient of Minnesota digital traffic.  He agreed; Dave sent him a KAM from the equipment bank (like the one you  have, maybe?  I forget) and he's in the process of getting the cables wired up now for his specific radio.

Again, congrats!

Luck Hurder, WA4STO
Title: Re: 2m antenna tuning
Post by: Geek on July 14, 2013, 05:41:17 PM
Congratulations are premature.  I acquired an antenna and it connected to WA2IMS, but. The successor hops did not happen so I did not get an email out.  I am giving it another shot later.

I also spent some time talking to a fellow who is promoting DStar for getting some email to function during events like Sandy.  Apparently they are having some success in Sussex County but have not been able to get much traction in neighboring counties.  I might want to give that a try as well.
Title: Re: 2m antenna tuning
Post by: WA4STO on July 14, 2013, 07:11:10 PM
Howdy again

I disagree!  Congrats are definitely in order.  The fact that a secondary connection didn't (yet) occur is not your fault. 

Your job, and that of your equipment is (in this case) a matter of connecting to the first station in the chain.  Anything beyond that is not something that you have any control over.

Wow, I sure remember the first time I actually made a connection on VHF packet.  Thought I'd gone to heaven.  :)

Best 73

Luck, WA4STO
Title: Re: 2m antenna tuning
Post by: Geek on July 15, 2013, 08:18:08 AM
Well, I am still not able to send an email, which was the whole point.  If it doesn't work now, will it work in a disaster scenario?  Maybe the DStar approach will work.