The RadioReference.com Forums - Antennas and Coax Forum http://forums.radioreference.com/ Discussion on the development and implementation of antennas for radio monitoring activities. en Sat, 21 Nov 2009 00:35:40 GMT vBulletin 60 http://forums.radioreference.com/images/misc/rss.jpg The RadioReference.com Forums - Antennas and Coax Forum http://forums.radioreference.com/ Antenna wire through windows? Questions. http://forums.radioreference.com/antennas-coax-forum/164911-antenna-wire-through-windows-questions.html Thu, 19 Nov 2009 23:28:23 GMT Here is my situation... I am located in a 3rd floor condo in Chicago and would like to run wire from an antenna sitting on my deck to my office about 30ft away. I would like to avoid running the wire through the walls (concrete and steel construction) and think it will be no problem to hang it... Here is my situation...

I am located in a 3rd floor condo in Chicago and would like to run wire from an antenna sitting on my deck to my office about 30ft away. I would like to avoid running the wire through the walls (concrete and steel construction) and think it will be no problem to hang it along the outside of the wall. Currently, this will be receive-only. I have a couple questions:

- What is the best way to run through the window?
- Do I have to worry about any performance decrease with that long of a length from Ant to radio?
- How can it be grounded? (no pipes, metal railing is screwed into brick without a contact to earth)

Thanks in advance ]]> Antennas and Coax Forum hackinstack http://forums.radioreference.com/antennas-coax-forum/164911-antenna-wire-through-windows-questions.html Help with identifying antenna http://forums.radioreference.com/antennas-coax-forum/164831-help-identifying-antenna.html Thu, 19 Nov 2009 04:36:18 GMT Can someone help me with identifying this antenna, I bought it from Antenna Warehouse several years ago and forgot the name of the Antenna, I know it's a,
Scanner antenna beam
Is it 8 elements or 16,

Any help appreciated,
Steve
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]]> Antennas and Coax Forum Saint http://forums.radioreference.com/antennas-coax-forum/164831-help-identifying-antenna.html Antennas Antennas Antennas Galore http://forums.radioreference.com/antennas-coax-forum/164829-antennas-antennas-antennas-galore.html Thu, 19 Nov 2009 04:28:07 GMT If it's an antenna, I guess they got it.

Antenna Experts - Fiberglass Collinear Stacked Dipole Discone Antenna Yagi Antenna Log Periodic Antenna Helical Antenna Jammer Antenna HF Broadband Antenna Marine Band Antenna Aviation Band Antenna Defense Band Antenna Satellite Tracking Antenna Ship

FLRAILMAN ]]> Antennas and Coax Forum FLRAILMAN http://forums.radioreference.com/antennas-coax-forum/164829-antennas-antennas-antennas-galore.html Antennas pros/cons http://forums.radioreference.com/antennas-coax-forum/164802-antennas-pros-cons.html Wed, 18 Nov 2009 22:43:16 GMT Hi I am doing a essay on different HF antenna types. And im trying to simplify this in a simple. positive pros list and a negative cons list on the different types. I know that everything makes a difference and affects the antenna etc etc so im trying to find simple charasteristics that is... Hi
I am doing a essay on different HF antenna types.
And im trying to simplify this in a simple.
positive pros list and a negative cons list on the different types.
I know that everything makes a difference and affects the antenna etc etc
so im trying to find simple charasteristics that is easy to explain to a normal civilian :)
including myself.

Broadband dipole Pros/Cons ???????

Vertical whip antenna Pros/Cons ????

Conical Monopole antenna Pros/Cons ????

Log Periodic Antennas Pros/Cons ????

I hope you can help me ]]> Antennas and Coax Forum quicksy12 http://forums.radioreference.com/antennas-coax-forum/164802-antennas-pros-cons.html multi-band mobile antenna recommendations http://forums.radioreference.com/antennas-coax-forum/164773-multi-band-mobile-antenna-recommendations.html Wed, 18 Nov 2009 15:39:03 GMT Hi Everyone,
I just bought a 396XT and plan to use it in my car. I want to purchase a good multi-band antenna, and I'll mount it on the passenger-side of the rear hatch on my Subaru Forester. The driver-side of the hatch is the home of my vhf/uhf transceiver stick. I'll mount the scanner antenna using a Diamond K412SNMO mount because it is adjustable in 2 dimensions.

I've read about the Austin Spectra and it looks appealing, but I've read comments where some users consider it a bit fragile. I was hoping to use as much of the scanner's freq range (25-1300) as possible.

Does anyone have any comments about the Spectra, good or bad, and can anyone offer other antenna recommendations?

I've looked at this so much I'm getting myself confused - TMI, I think.

thanks in advance/73
w2edv
:confused: ]]> Antennas and Coax Forum w2edv http://forums.radioreference.com/antennas-coax-forum/164773-multi-band-mobile-antenna-recommendations.html Off Center Dipole http://forums.radioreference.com/antennas-coax-forum/164742-off-center-dipole.html Wed, 18 Nov 2009 01:40:13 GMT Few questions regarding homebrew off center dipole. I have one made of ½” copper pipe with pvc T, balun and end caps. I also have made one with just wire and balun. Question is ½” copper ok? Or should it be ¾”. Would there be any difference? And for the wire dipole stranded wire or sold wire 12... Few questions regarding homebrew off center dipole. I have one made of ½” copper pipe with pvc T, balun and end caps. I also have made one with just wire and balun. Question is ½” copper ok? Or should it be ¾”. Would there be any difference? And for the wire dipole stranded wire or sold wire 12 gauge. I used solid. Just looking for some input and experiences form users. Thanks ]]> Antennas and Coax Forum oneworld http://forums.radioreference.com/antennas-coax-forum/164742-off-center-dipole.html Help fixing R.S. Mag Mount Antenna http://forums.radioreference.com/antennas-coax-forum/164693-help-fixing-r-s-mag-mount-antenna.html Tue, 17 Nov 2009 13:14:05 GMT I've taken a couple of pictures from other posts to try to see if I can explain the problem I'm having with
my Radio Shack mag mount antenna. Mine is loose between the black plastic base and the top chrome
piece. When I go into the bottom all I see is a rivet which makes sense by looking at the picture from
izzjy4's pictures he posted. But I can't seem to figure out how to separate the top and bottom parts,
mine just spins freely....maybe I'm missing something simple here but I'd appreciate any input as
to how I can get it apart so I can clean and re-tighten everything.
Thanks!
N6RDC
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]]> Antennas and Coax Forum N6RDC http://forums.radioreference.com/antennas-coax-forum/164693-help-fixing-r-s-mag-mount-antenna.html Discone vs Diamond http://forums.radioreference.com/antennas-coax-forum/164679-discone-vs-diamond.html Tue, 17 Nov 2009 04:27:33 GMT I Have a Diamond antenna on my 106,` would there be any difference in reception/distance if I Got a Discone antenna? I Have a Diamond antenna on my 106,` would there be any difference in reception/distance if I Got a Discone antenna? ]]> Antennas and Coax Forum Wahoos4Life http://forums.radioreference.com/antennas-coax-forum/164679-discone-vs-diamond.html Identifying Antenna http://forums.radioreference.com/antennas-coax-forum/164624-identifying-antenna.html Mon, 16 Nov 2009 16:53:20 GMT Does anybody recognize this antenna? If so, what band is it designed for? I saw this antenna on an Italian police car in Rome. I didn't have my scanner, so I never figured out what frequencies were in use. Thanks.
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]]> Antennas and Coax Forum JoeH http://forums.radioreference.com/antennas-coax-forum/164624-identifying-antenna.html Band Pass Filter http://forums.radioreference.com/antennas-coax-forum/164544-band-pass-filter.html Sun, 15 Nov 2009 12:47:01 GMT Im hoping someone with a technical background can help me in this field. Listening in the New York Metro area naturally brings intermod and front end overloading easily in open scanning modes. I see that Scannermaster has both the VHF band pass filter and the FM Notch Filter. Does anyone have... Im hoping someone with a technical background can help me in this field. Listening in the New York Metro area naturally brings intermod and front end overloading easily in open scanning modes. I see that Scannermaster has both the VHF band pass filter and the FM Notch Filter. Does anyone have suggestions on if any of these would be useful in a mobile scanning application where its a 396XT connected to a mobile antenna in the car?

Any insight would be appreciated

Thank you ]]> Antennas and Coax Forum BFIFM790 http://forums.radioreference.com/antennas-coax-forum/164544-band-pass-filter.html Radio Shack ferrites measured! http://forums.radioreference.com/antennas-coax-forum/164361-radio-shack-ferrites-measured.html Fri, 13 Nov 2009 03:54:35 GMT I use a number of RS ferrite snap-on chokes as either feedpoint baluns / chokes, or as a way to tune the common-mode of the feedline as a 1/4 wave element. I measured them with an MFJ 259B antenna analyzer with a very small length of RG-58 with the braids and center conductor twisted together on... I use a number of RS ferrite snap-on chokes as either feedpoint baluns / chokes, or as a way to tune the common-mode of the feedline as a 1/4 wave element.

I measured them with an MFJ 259B antenna analyzer with a very small length of RG-58 with the braids and center conductor twisted together on each end, and attached to the shield and antenna posts of the analyzer with the bead snapped on. I only measured up from about 30 mhz, where there was no reactive component (X) present when the bead was snapped on.

This is the best I could do, and on some of the chokes, I did not have an absolutely tight fit. I'm sure someone can do a better job than I did here as I don't have any fatter jumpers available - and I'm not cutting up my existing feedline. :)

Problem is, how may of these do you need? Most references to the choking impedance needed to make a good feedpoint choke on symetrically-fed dipoles vary from 500 - 1000 Z, with 1000 ohms preferable.

For my quarter-wave common-mode elements where I purposely use this "feature" of coax, you need around 3000 ohms or more! (See my other antenna notes about the half-sloper about how to get around this and use less chokes.)

So how many do you need, ie what is the value of the individual chokes and at what frequencies?

RADIO SHACK 273-105 (or 273-0105)
Type-43 material

FREQ R
------- ----
30 150
45 195
55 245
70 260
88 270
108 236
118 221
125 210
136 189
146 175
160 165
175 141



RADIO SHACK 273-069
(I'm not sure what mix this is)

FREQ R
------- ----

88 245
108 375
118 400
137 377
146 337
160 288
170 250

This 273-069 was a very tight fit for the RG-58. Could that tightness mean that my earlier measurements are a bit on the low side for the 273-105 ? Probably, but maybe someone can do better than with my test setup.

At any rate, for the 105's, and for that matter most of my other type-43 ferrite material chokes I had laying around, the results were about the same. So to be conservative, for projects that use the type-43's, I'll mentally calculate that each has about 200 ohms and for good measure, add one more.

Not very scientific, and I wish I had the equipment to do a better test. ]]> Antennas and Coax Forum hertzian http://forums.radioreference.com/antennas-coax-forum/164361-radio-shack-ferrites-measured.html Antennas used by the USFS http://forums.radioreference.com/antennas-coax-forum/164349-antennas-used-usfs.html Fri, 13 Nov 2009 02:43:56 GMT Does anybody know the manufacturer/model of the antennas used by the USFS on their vehicles? I've seen pictures from different Natl Forests vehicles and they look like that
Chevrolet Tahoe LS on Flickr - Photo Sharing! ]]> Antennas and Coax Forum N467RX http://forums.radioreference.com/antennas-coax-forum/164349-antennas-used-usfs.html J-Pole coax center to short or long element? http://forums.radioreference.com/antennas-coax-forum/164336-j-pole-coax-center-short-long-element.html Thu, 12 Nov 2009 23:31:03 GMT I have seen different designs for the j-pole and cant understand why they are all basically the same EXCEPT some designs specify to attach the center of the coax to the short stub and some say to attach it to the longer part of the antenna?? Comments? I have seen different designs for the j-pole and cant understand why they are all basically the same EXCEPT some designs specify to attach the center of the coax to the short stub and some say to attach it to the longer part of the antenna?? Comments? ]]> Antennas and Coax Forum conve36 http://forums.radioreference.com/antennas-coax-forum/164336-j-pole-coax-center-short-long-element.html wilson electronics cellular trucker antenna http://forums.radioreference.com/antennas-coax-forum/164256-wilson-electronics-cellular-trucker-antenna.html Thu, 12 Nov 2009 02:02:47 GMT Has anyone ever used a wilson electronics cellular trucker antenna mod #301101 with a digital scanner to monitor a 700 or 800 mhz p25 system? I was just wondering if it would work better than a stock antenna or a radio shack 800mhz duck. Here is a link: Cell Phone Antennas and Cell Phone... Has anyone ever used a wilson electronics cellular trucker antenna mod #301101 with a digital scanner to monitor a 700 or 800 mhz p25 system?
I was just wondering if it would work better than a stock antenna or a radio shack 800mhz duck.

Here is a link:
Cell Phone Antennas and Cell Phone Boosters at Wilson Electronics

thanks ]]> Antennas and Coax Forum kc9neq http://forums.radioreference.com/antennas-coax-forum/164256-wilson-electronics-cellular-trucker-antenna.html diamond rhf40 http://forums.radioreference.com/antennas-coax-forum/164214-diamond-rhf40.html Wed, 11 Nov 2009 18:51:35 GMT How well does this antenna work and how do you use it for portable use with a mid size hh scanner. Will be using it on a br330t. Would I be better off getting a rh77ca antenna. How well does this antenna work and how do you use it for portable use with a mid size hh scanner.
Will be using it on a br330t. Would I be better off getting a rh77ca antenna. ]]> Antennas and Coax Forum mbahcall http://forums.radioreference.com/antennas-coax-forum/164214-diamond-rhf40.html Good Scanner Antenna? http://forums.radioreference.com/antennas-coax-forum/164212-good-scanner-antenna.html Wed, 11 Nov 2009 18:10:42 GMT I am looking at buying myself a new scanner antenna to run two scanners off of. The antenna's that I am looking at are the MFJ-1868 and Radio Shack 20-043. I want a antenna that receives air band and 800 well. The antenna's look about the same as I can tell from the pictures. Does anyone have any info on these? which would you prefer? Thanks for the insight... ]]> Antennas and Coax Forum btlacer http://forums.radioreference.com/antennas-coax-forum/164212-good-scanner-antenna.html Grounding (?) an attic-mounted J Pole http://forums.radioreference.com/antennas-coax-forum/164207-grounding-attic-mounted-j-pole.html Wed, 11 Nov 2009 17:19:23 GMT I want to attic-mount an Arrow J Pole for use with a Yaesu FT-7900 (2M/ / 70 cm). Does an attic setup such as this one have to be grounded? I recall reading a thread that suggested grounded an attic-mount antenna.

If this needs to be grounded, what's the proper way to ground this?

Thanks. I appreciate the feedback. ]]> Antennas and Coax Forum KJ6CFU http://forums.radioreference.com/antennas-coax-forum/164207-grounding-attic-mounted-j-pole.html My Antenna Installed http://forums.radioreference.com/antennas-coax-forum/164206-my-antenna-installed.html Wed, 11 Nov 2009 17:10:32 GMT Thanks for everybody's help.

Comet UHF VHF GP-3 antenna
5' EMT pipe primed & painted white
18" Clearance heavy duty wall mount
100' of CNT-400
~20' gauge 6 ground wire to a 8' 5/8" ground rod
FT-7800 & FT-60r
~300' above sea level
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]]> Antennas and Coax Forum BonziBuddy http://forums.radioreference.com/antennas-coax-forum/164206-my-antenna-installed.html BC560XLT antenna http://forums.radioreference.com/antennas-coax-forum/164158-bc560xlt-antenna.html Wed, 11 Nov 2009 00:51:43 GMT We are an older couple and have a BC560XLT scanner. We were both on the local volunteer fire department about twnety years ago and my wife still likes to listen to what is happening. One night it quit working so we put it up. I finally found out where I couild buy a new power supply for it and... We are an older couple and have a BC560XLT scanner. We were both on the local volunteer fire department about twnety years ago and my wife still likes to listen to what is happening. One night it quit working so we put it up. I finally found out where I couild buy a new power supply for it and tried it out tonight and it works.
The problem is I think we (I) through away the antenna. I decided to check this forum and see what kind of antenna everyone recommened. I seen where some liked the Radio Shack 20-161, the Radio Shack
20-006, or the Diamond scanner antenna. I just don't know what kind of connector it takes, I don't think it is a BNC. I think it is a Motorola plug type. The antennas I am looking at all have BNC connections and I don't know what to buy so I can plug it in. Can someone point me in the direction of a good antenna that plugs into the BC560XLT? I would like to pick up signals at least 20 miles away.
Also does a base antenna have to be grounded? I thought about buying an outside antenna and hanging it up with a piece of rope or something outside in the garage from the ceiling
Can anyone help an old guy out so he can get his wife fixed up to listen again?
Thanks, I so much appreciate it. ]]> Antennas and Coax Forum arbutler2000 http://forums.radioreference.com/antennas-coax-forum/164158-bc560xlt-antenna.html Antenna Springs and Coil http://forums.radioreference.com/antennas-coax-forum/164150-antenna-springs-coil.html Wed, 11 Nov 2009 00:06:43 GMT Mmmkay I have wanted to ask this for a while. I have a 3.5inch spring and a 3 inch spring. What would these be used with? Iv got 2 VHF antennas both half wave for 142.500mhz Also have a Larson NMO 150 and a Maxrad MHB5802 mounts Now would these spings go with these mounts and antennas? ... Mmmkay

I have wanted to ask this for a while. I have a 3.5inch spring and a 3 inch spring.
What would these be used with?
Iv got 2 VHF antennas both half wave for 142.500mhz
Also have a Larson NMO 150 and a Maxrad MHB5802 mounts

Now would these spings go with these mounts and antennas?

Or what would these all be used for

This would be for RX and TX ]]> Antennas and Coax Forum Muxlow http://forums.radioreference.com/antennas-coax-forum/164150-antenna-springs-coil.html Scantenna ST2 Matching Transformer http://forums.radioreference.com/antennas-coax-forum/164131-scantenna-st2-matching-transformer.html Tue, 10 Nov 2009 20:11:35 GMT Currently have one of these on the antenna

It's been up here for about 6 years now and I am thinking it's time for a new one. Anyone know of a place to get a heavy duty version? ]]> Antennas and Coax Forum webstar22 http://forums.radioreference.com/antennas-coax-forum/164131-scantenna-st2-matching-transformer.html Multiples antenna with multiples scanner http://forums.radioreference.com/antennas-coax-forum/164122-multiples-antenna-multiples-scanner.html Tue, 10 Nov 2009 17:22:25 GMT Hi

I'm searching for an antenna switch that will allow me to select 1 of about 3 antennas. I also have 4 scanners, and would like to be able to connect all to the same switch. Is there a crosspoint switcher of some sort out there, that would allow me to point different antennas at different rigs?

I wanted to be able to run 2 rigs at the same time on different antennas.

The only thing i found is this : https://www.mfjenterprises.com/Produ...ctid=MFJ-1700C but the frequency range is too low

I already have the alpha delta Delta-4B/N switch but let me use just one antenna at a time.

thank

Mrscanner2008 ]]> Antennas and Coax Forum mrscanner2008 http://forums.radioreference.com/antennas-coax-forum/164122-multiples-antenna-multiples-scanner.html Max Systems 8HH antenna http://forums.radioreference.com/antennas-coax-forum/164065-max-systems-8hh-antenna.html Mon, 09 Nov 2009 22:30:25 GMT I have been looking for a better indoor antenna for my Uniden BC296D. I purchased one of the Radio Shack 800 MHz rubber ducks and found that was an improvement over the stock Uniden antenna on 800 MHz however I wanted something better. Several folks claimed the Max Systems 8HH antenna was good. ... I have been looking for a better indoor antenna for my Uniden BC296D. I purchased one of the Radio Shack 800 MHz rubber ducks and found that was an improvement over the stock Uniden antenna on 800 MHz however I wanted something better. Several folks claimed the Max Systems 8HH antenna was good. Several internet retailers claim that the 8HH is the "serious" antenna for 800 MHz monitoring.

I received an 8HH today and am quite disappointed. In fact, both the stock Uniden antenna and the Radio Shack 800 MHz antenna performed better than the Max Systems 8HH.

Several posters also noted that the 8HH is supposed to have hardline between the BNC connector and the antenna elements. Whatever the manufacturer is using is certainly not hardline as it will barely support the antenna. ]]> Antennas and Coax Forum skile http://forums.radioreference.com/antennas-coax-forum/164065-max-systems-8hh-antenna.html High SWR http://forums.radioreference.com/antennas-coax-forum/164022-high-swr.html Mon, 09 Nov 2009 12:26:06 GMT I have a Kenwood 7180H with a Comet CA-2x4srb antenna in my vehicle. While on 2 meters and low power (10w), my SWR is 1.2. When I go to high power (50w), my SWR jumps to from 10 to infinity. Should there be such a drastic difference in SWR? Any ideas? I have a Kenwood 7180H with a Comet CA-2x4srb antenna in my vehicle. While on 2 meters and low power (10w), my SWR is 1.2. When I go to high power (50w), my SWR jumps to from 10 to infinity. Should there be such a drastic difference in SWR? Any ideas? ]]> Antennas and Coax Forum salcia http://forums.radioreference.com/antennas-coax-forum/164022-high-swr.html handheld antenna http://forums.radioreference.com/antennas-coax-forum/163969-handheld-antenna.html Sun, 08 Nov 2009 19:15:51 GMT want to build a general purpose receiving antenna for a radio shack handheld scanner.anybody have any ideas? i listen to anything that i can,zeke want to build a general purpose receiving antenna for a radio shack handheld scanner.anybody have any ideas? i listen to anything that i can,zeke ]]> Antennas and Coax Forum nascarzeke http://forums.radioreference.com/antennas-coax-forum/163969-handheld-antenna.html house base station antenna grounding http://forums.radioreference.com/antennas-coax-forum/163923-house-base-station-antenna-grounding.html Sun, 08 Nov 2009 04:34:44 GMT Hello fellow listeners:

I just mounted a Bearcat antenna on a 3/4 " 10 foot high piece of galvinized conduit along side of my house - putting the antenna about 5-6 feet above roof line....I don't "do" roofs so I couldn't get any higher or believe me, I would have....I live in a valley in Northern New Jersey (Wanaque (very little reception due to mountains all around us)) where we get maybe 6-8 vigorous thunderstorms a year with some nearby lightning strikes and my hosue is surrounded by trees that average 60-80 feet in height. We've never been "hit" by lgihting nor have the trees, so far as we know.

Question is this: I went to Home Depot and picked up an 8 foot copper ground rod, some # 4 open copper strand wire, and a a few clamps. Help at Home Depot told me to drive the copper rod (as much of the eight feet) into the ground for good protection. If cannot do so due to rocks (and we have a lot of 'em) - go as deep possible, cut the excess above ground and drive in a second rod and clamp that to the first rod, using the same # 4 wire.
So now I will have a "ground field" of sorts, (I guess).....

First: will this work to protect the house in case the antenna takes a lighting hit, either direct or "fragmented" from a hit to a nearby treee?

Second, do I need additional ground or surge protection at the point of entry to the house and for the coax cable as well?

I'm not protecting anything too valuable in the way of my scanner - it's a Bearcat BC898T - but I'm attempting to protect everything in my life (and my wife) with the house and all the other electronic goodies we have, lights, refrigerator, microwave and stove not counted.

I got into this because we never had a big ole' stick of metal sticking up into the air above our humble abode before and prior to next spring when that occassional thunder-blaster rolls through, I want to be ready for the worst possible scenario.....

Any help - much appreciated - as usual - I find that there's a lot of wisdom out here and you're all mightly generous in sharing same.....

Thanks folks!

Happy listening.....

Bill ]]> Antennas and Coax Forum billybobears http://forums.radioreference.com/antennas-coax-forum/163923-house-base-station-antenna-grounding.html Specific RR HH antenna questions http://forums.radioreference.com/antennas-coax-forum/163880-specific-rr-hh-antenna-questions.html Sat, 07 Nov 2009 14:45:27 GMT Had a couple of questions. I mainly use two handhelds for RR monitoring a Pro96, and 346XT. I currently use the Diamond RH77CA on my 346, and a Maldol W100RX (telescoping) on the 96. Are there any other HH antennas that really shine in the RR bands, or upper end of VHF-high(160-174)? The two... Had a couple of questions. I mainly use two handhelds for RR monitoring a Pro96, and 346XT. I currently use the Diamond RH77CA on my 346, and a Maldol W100RX (telescoping) on the 96.

Are there any other HH antennas that really shine in the RR bands, or upper end of VHF-high(160-174)?
The two I use are GREAT, but was hoping for a little more distance for some spine-lines I listen to. I know I could go to a base scanner, and put up an outdoor antenna, but really just wanted to make sure there were not any HH ones I might try, or may have missed.

Mods. if this is more RR forum specific, I apologize, just wasnt sure which forum to post it in. Thanks for any help, Mike ]]> Antennas and Coax Forum Haley http://forums.radioreference.com/antennas-coax-forum/163880-specific-rr-hh-antenna-questions.html <![CDATA[VHF indoor "half sloper"]]> http://forums.radioreference.com/antennas-coax-forum/163870-vhf-indoor-half-sloper.html Sat, 07 Nov 2009 08:11:30 GMT Here's something I built (with a picture included) that is mostly of interest to indoor / attic users.

I adapted an HF quarter-wave sloper, or "half sloper" for VHF use, and instead of using a grounded tower, I faked the vertical section with chokes.

Half-slopers are vertically polarized antennas, and have some gain in the direction of the slope. Mine definitely does.

1) Attach a quarter wave (234 / freq mHz * 12 = inches) of wire to the center conductor of the transmission line. Here, I used the center conductor of an F-chassis connector to solder to, and screwed the RG-6 into the chassis connector. Nothing is connected to the shield.

This wire slopes down towards the ground at a 45-degree angle. Be sure you don't short it out to the braid when you bend it downward. If you need to, you can support the sloping wire with cord, dental floss (no kidding!) whatever to maintain at *least* a 45-degree downward angle. You can bend it downwards even further, perhaps 60 degrees downwards max before things start to fall apart, as the impedance drops when you bring the sloping wire closer to the vertical section.

(antenna height, angle of the slope, element lengths are all tunable for transmitting duties that need absolutely low swr.)

2) Hang the top of the coax feedpoint near the top of the ceiling, rafters, eaves, whatever.

3) At the quarter-wave point down from the end of the coax, (234 / f Mhz * 12) I attached about 6 snap-on RF chokes (RS #273-0105). This tunes the common-mode of the coax to emulate a quarter-wave element. Forget about any sort of "velocity factor" compensation, as VF only applies to the differential-mode, or inside part of the coax. Yes, there is a very small amount on the outside due to the jacketing, but for rx-only we're starting to split hairs. :)

Compared to a full-sized vhf dipole, this really saves a lot of space up in the attic, and the feedpoint being at the top helps keep the antenna further away from attic clutter.

It was resonant in the air-band when I used 22-inches for both the sloping wire and the start of where the chokes snapped-on. However, I'm using a short run of 75 ohm RG-6 and my SWR meter is designed for 50 ohms so very precise measurements are off. The scanner likes it just as much as my dipole however, although now I have some directivity and a bit of gain.

I don't know how to model a ferrite-choked transmission line used as an antenna element in EZnec, but it does seem to be holding to the textbook descriptions for HF half-slopers.

Note that I tried using a separately cut quarter wave wire attached to the shield at first, but the system was just too unstable on the swr meter, and I didn't feel like devoting my life to it. :) So on go the chokes instead.

Ok, it isn't a world-beater antenna, but it might be a nice alternative if you need the features.
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]]> Antennas and Coax Forum hertzian http://forums.radioreference.com/antennas-coax-forum/163870-vhf-indoor-half-sloper.html Is this project to ambitious? http://forums.radioreference.com/antennas-coax-forum/163868-project-ambitious.html Sat, 07 Nov 2009 07:57:03 GMT I'd like to take this antenna , build it and add an element for CB reception as well as an element for the 40-50 mhz range. Come to think of it an element for MILAIR would not be bad as well.

Now , when it comes to building an antenna, I'm a complete newbie. I'm the first to admit it. But I am handy and from looking at the plans I know I can build it stock.

My question is

a. is adding elements for the 3 bands I mentioned a possibility

b. if so how and what lengths and angles would be required

I know it would probably be easier to just buy an antenna in the freq ranges I want but where is the fun in that? :)

Draf ]]> Antennas and Coax Forum Drafin http://forums.radioreference.com/antennas-coax-forum/163868-project-ambitious.html Wideband VHF antenna http://forums.radioreference.com/antennas-coax-forum/163836-wideband-vhf-antenna.html Fri, 06 Nov 2009 23:25:48 GMT Does anyone have experience using these VHF antennas that listed as "wideband coverage" such as the following:

Antenex ADB150 [ADB150] - $24.95 : The Antenna Farm :: , Your Two Way Radio Source!
Larsen WBQC [WBQC] - $29.95 : The Antenna Farm :: , Your Two Way Radio Source!

These antennas are claiming approximately 20mhz of usable bandwidth. Other antennas i've seen are typically in the 4-5mhz range.

I'm looking for an option that would allow me to efficiently transmit between 150-160mhz. This particular antenna will be on an L-bracket mount on the front passenger side fender. I'll be using a Midland Olympian radio that puts out 50watts.

Any thoughts or advice would be appreciated. ]]> Antennas and Coax Forum mjthomas59 http://forums.radioreference.com/antennas-coax-forum/163836-wideband-vhf-antenna.html