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Author Topic: "Best" Antenna Length for New Mobile Installation  (Read 12280 times)
KF5QJV
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« on: October 14, 2013, 10:03:26 AM »

I'm struggling with antenna selection for a new 2M/70 installation in a 2008 Toyota Tacoma.  My uncertainty is largely around 1/4 wave vs. 1/2 wave vs. 5/8 wave.  I've heard/read comments to the effect of "longer is not necessarily better," depending upon geographic location, but I always thought more gain was better; and, it seems more length generally means more gain.

I live in the Houston area but approximately 20 miles from downtown, so I'm neither in the "city" nor way out in the "country."  I'm inclined to consider this predominantly suburban location as my primary area of operation, but the reality is that I'll likely be operating within the city and in more rural areas (e.g., to/from Austin/San Antonio) as well.

Assuming a mounting point at the center of the roof of the cab would be significantly more performant than any other location, this is where I intend to mount the antenna via a permanent NMO mount (if similar performance may be realized using a lip mount on the hood, please advise).  I've been leaning toward the Comet-NCG CA-2X4SRNMO antenna for its high gain (and good reviews), but how much would I really be compromising if I were to go with something shorter like their B-10 or SBB-2?  I like the practicality of a shorter antenna but not at any appreciable expense in performance.

For what it's worth (and without necessarily inciting a radio debate as part of this thread), I'm considering either the IC-2820H or FT-8800R radios.

Any thoughts are greatly appreciated!
Rob
KF5QJV
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K6LCS
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« Reply #1 on: October 14, 2013, 10:30:14 AM »

>> ... but I always thought more gain was better; and, it seems more length generally means more gain.

I just recently went from a unity gain antenna to one with a little gain. Stupidest thing I have done in a while. I live in a valley (as do many Southern Californians), surrounded by hilltop repeater systems. All was well with little or no gain antenna ... but add some gain, and I consistently hear a station on the same freq as a local machine - from MEXICO.

SO .. longer and more gain for a mobile rig is not necessarily the best way to go. Only you can answer what is "best" for you in your environment.

>> ... Assuming a mounting point at the center of the roof of the cab would be significantly more performant than any other location ...

For ME in MT region, that is NOT a significant point. And, put a long antenna on your roof, and you'll never drive through Jack in the Box again without pain, nor drive into a parking structure.

Do you have the 4-door model? If so, I'd use a quality lip mount there ... like a K400.

And if you do not have a camper shell and the read windows are not metallic glass. consider the Larsen KG through-the-glass systems. Unlike lesser-priced knock-offs, they DO work very well.

Clint K6LCS

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Clint Bradford, K6LCS
http://www.work-sat.com
N6AJR
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« Reply #2 on: October 14, 2013, 11:41:14 AM »

If you are just talking to repeaters, then a 10 inch tall mounted on a trunk lip mount will be just fine.  if you can stand outside the car with an HT then a small antenna will work.
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M6GOM
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« Reply #3 on: October 14, 2013, 12:15:20 PM »

I'm struggling with antenna selection for a new 2M/70 installation in a 2008 Toyota Tacoma.  My uncertainty is largely around 1/4 wave vs. 1/2 wave vs. 5/8 wave.  I've heard/read comments to the effect of "longer is not necessarily better," depending upon geographic location, but I always thought more gain was better; and, it seems more length generally means more gain.

Any thoughts are greatly appreciated!
Rob
KF5QJV

The difference in gain between a 1/4 wave and a 5/8 wave is negligible, barely a couple of dB...certainly not enough to make it a make or break decision on gain alone.

The 5/8 wave will put the maximum gain out at a lower angle than the 1/4 wave which may or may not be beneficial depending on the topography and heights of repeater above where you are that you're likely to encounter the most.

I used a 5/8 wave 2m antenna and interchanged between a 1/4 wave. Static I noticed little difference even to a repeater 50 miles away. On the move with the 5/8 wave, the antenna was swaying about due to the flexibility of the whip which meant the RX signal was forever rising and falling in strength - I believe its called picket fencing? The shorter 1/4 wave whip was rigid and didn't suffer from it.
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K5LXP
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« Reply #4 on: October 14, 2013, 01:03:01 PM »

Quarter waves are not as likely to get ripped off in the car wash.  

Carrying the thought a step further, try the quarter wave first.  They're all of what, $10?  Run it for a while and see what you think.  With an NMO mount you can always swap something else in later if you want to.

Mark K5LXP
Albuquerque, NM
« Last Edit: October 14, 2013, 01:10:30 PM by K5LXP » Logged
AC4RD
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« Reply #5 on: October 14, 2013, 04:52:20 PM »

With an $8 dual-band 3/8x24 2m/440 whip, quarterwave for both bands, I can hit a repeater 25 miles away pretty easily with 20 watts.  The repeater site is up high, and the terrain is mostly flat.  But a quarterwave is (as K5LXP hinted) a good way to start.  And inexpensive besides!  73 GL!  --ken
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KF5QJV
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« Reply #6 on: October 15, 2013, 10:45:31 AM »

Thanks for all the feedback.  I'll likely do the 1/4 wave now.  I will mostly be using repeaters, and this makes a lot of sense.  I guess I'm used to the relatively low performance of my HT and just have little/no experience with a real mobile rig, so I was thinking I needed something much bigger.  Despite having replaced my Yaesu VX-8's stock ducky with a pretty decent Diamond SRH320A, I've been a little surprised by the reception.

Rob KF5QJV
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K6LCS
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« Reply #7 on: October 15, 2013, 11:56:07 AM »

The concept of "line of sight" is an amazing one. I remember one of the first reception reports from a newly launched satellite a couple years ago was from a gentleman using his VX-8R and the STOCK DUCK! Yes - 250-500mW from 500+ miles away, and the stock duck on a ham HT ...

Clint K6LCS
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Clint Bradford, K6LCS
http://www.work-sat.com
KF5QJV
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Posts: 6




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« Reply #8 on: October 15, 2013, 06:04:57 PM »

Clint, I just checked out your site, and I'm surprised I hadn't come across it before now.  I'm still relatively new to amateur radio, but working satellites has been one of my primary interests.  I've had an Arrow, just for this purpose, for some time, but I just haven't gotten around to using it.  It seems I may be a little late to the SAT game, from all I've read, but I hope I'm wrong!  I've bookmarked your site and will certainly be referring to it in the future.

Rob KF5QJV
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K6LCS
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« Reply #9 on: October 15, 2013, 06:14:30 PM »

Thanks for the kind words. (Don't tell anyone, but I still have AO-51 and AO-27 programmed in my sat HTs ... (grin).) We have AMSAT-Fox to look forward to ... the "finicky" SO-50 (best worked true full duplex) ... packet bursts from the ISS ... there's still plenty to do with minimal equipment and space objects!

Make dure you report your "hearings" (and reports of NOT hearing a sat when you thought you should!) at the Live OSCAR Sat Status Site at ...

http://oscar.dcarr.org/

Clint K6LCS
909-241-7666 - cell

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Clint Bradford, K6LCS
http://www.work-sat.com
K5BBC
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Posts: 24




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« Reply #10 on: October 16, 2013, 05:34:55 PM »

" I'm considering either the IC-2820H or FT-8800R radios."

I've been using 2820s for about three years, and love them. I've used the FT8800R, and while I'm sure it's a good radio, I think the 2820 is far superior in switch and menu function, and %100 better display.

I've done the 1/4 wave 5/8 wave thing too.  I saw a small difference in flatland remote areas. Biggest difference I got in reports from others was on the UHF side using a gain antenna.

73
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KA4NMA
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« Reply #11 on: October 16, 2013, 07:32:43 PM »

Check out k0bg.com. Alan has one of the best mobile sites around.

Randy ka4nma
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K1CJS
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« Reply #12 on: October 17, 2013, 02:01:07 PM »

Your decision to use the 1/4 wave is probably going to work out the best.  As most have said, gain antennas can work better--and they can work worse.  If most of the repeaters you want to work are in a twenty to thirty mile radius of you, there is little need for more than a simple 1/4 wave whip--AND you won't have to worry as much if you do use a roof mount.
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KK4CRY
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« Reply #13 on: October 18, 2013, 01:29:25 AM »

I placed a NMO mount from Breedlove in center of my roof and Larson 2/70b, now to figure out what to do about these Composite beds damn toyota
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M6GOM
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« Reply #14 on: October 18, 2013, 09:09:28 AM »

For VHF/UHF I don't think you need to worry about the truck bed. There's plenty of metal in the roof to get the job done. HF is a different matter entirely.
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