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Old 11-05-2013, 6:41 PM
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Unhappy Not receiving lowband

I have been trying for the past 3 weeks to pick up lowband and have gotten nothing. I am using a radio shack pro 2036 and 40 foot of lmr coax ran outside and to the roof. The antenna I am using is the top fiberglass section of a antron 99 cb base antenna. What am I doing wrong? I am located in western kentucky if that makes any difference. Thanks for any help anyone can give me.
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Old 11-06-2013, 1:24 AM
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Default Low Band Skip

First be sure the antenna and tradio are working by trying to receive a low band fire dept or known low band station. On Nove 2nd 3rd and 4th all i was receiving here was 29.60 from colorado and 29.68 from
Puerto Rico sometimes in Spanish but mostly in English by canadian stations VEs and w4 stations in North Carolina as well as an island station and western stations. The band seems to be opening close to or above 35MHz and seems everydan to get a little higher. today i didnt try listening joe

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I have been trying for the past 3 weeks to pick up lowband and have gotten nothing. I am using a radio shack pro 2036 and 40 foot of lmr coax ran outside and to the roof. The antenna I am using is the top fiberglass section of a antron 99 cb base antenna. What am I doing wrong? I am located in western kentucky if that makes any difference. Thanks for any help anyone can give me.
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Old 11-06-2013, 5:24 PM
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Well that's all I am interested in is the low band police and fire departments. I have a lot of low band frequencies programed and scanning but not getting anything
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Old 11-06-2013, 7:06 PM
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VHF lo band propagation, unlike HF, doesn't happen every day. There are certain ionospheric (and sometimes weather) conditions that cause VHF lo to propagate further than normal.

But let's start with the antenna. I would check the connection to the fiberglass whip to make sure you have a good solid connection. The A99 used a series of tuning collars to make it resonate on the 27 Mhz band. Just connecting to the fiberglass whip does not disconnect the tuning circuits that are below it. To just use the whip you would need to physically break that connection, and I don't think you want to do that, frankly. As just a receive antenna, performance will very likely degrade above 30 Mhz or so (perhaps a little higher than that but not by much. Hams do use this antenna up to just under 30 Mhz with tuners and the like, but it's probably not very efficient much above that).

Propagation on VHF lo depends on either solar or weather conditions, particularly so during sunspot maximum. The problem is that it's been very widely reported that this is among the weakest maximum in 50-100 years. So hams hoping to chase 50 Mhz (6 meter) DX have been sorely disappointed. What this means is that the maximum usable frequency (as a broad definition, the highest frequency that will propagate between 2 points, otherwise known as MUF) has been much lower than one would expect. Put another way, if the MUF for a particular time of day is only running around 20 Mhz, if you're listening at 40 Mhz, chances are you're not going to hear much DX.

Weather conditions can play a significant role - particularly if the weather is rather violent. When I lived in a top floor condo, I had a 40 Mhz vertical dipole in my attic attached to an old Regency TS2, and right around when severe TStorms or snow were approaching, signals from Tennessee, Georgia and Florida were regular visitors.

You might profit from doing a little homework using Google or your favorite search engine on 6 meter propagation. While this is the very top of the VHF low band, the techniques and discussions are quite applicable for the rest of the band as well. There are maps out there that allow you to view the MUF in a given area. I'm sure some folks here can recommend some simple sites - the ones I have tend to be a little much for a newcomer.

A good indicator would be to listen for any VHF lo band traffic in your area. I can remember many times using an old Regency handheld and a 6 meter mag mount, listening to California during the last solar maximum on 39 Mhz (where our local State Police can be found). If you start to hear stations - particularly mobiles - that you didn't hear before, chances are that some enhancement is taking place. I would also put in 29.60 (10 meter FM simplex) and 52.525 (6 meter FM simplex). These 2 are well known ham frequencies.

Another good rule of thumb is to loosen that squelch. Skip often 'builds' - it may start off as a weak, scratchy signal and get stronger as the event progresses.

As for an antenna - if it were me, I'd build a vertical dipole for 40 Mhz (the length of each element would be the famous 234 / F(mhz) . No need to fool around with shortening due to ground effects and so forth - we're not transmitting here). Use the techniques found in our Off Center Fed Dipole article. Make very sure that the coax is running perpendicular away from the antenna for a good bit before dropping down - this prevents the coax from interacting with the antenna.

Homebrewed Off-Center Fed Dipole - The RadioReference Wiki

HTH....Mike
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Last edited by ka3jjz; 11-06-2013 at 8:21 PM..
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Old 11-10-2013, 4:28 PM
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Mike, the design that you posted for the OCFD, are those the correct length for each leg? Or do they need to be longer? Do I mount the antenna verticaly or horizontaly? Thanks for your help!!!!
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Old 11-10-2013, 4:35 PM
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As I wrote in my message, you would need to change the length of the 2 legs using the formula I gave. As shown in the pic, it's not really tuned for the VHF lo band area. And as shown, it would be mounted vertically

There's also a wire version of the dipole you can play with in that same article - that way you can build one on the cheap to see if it fits your needs. Get it up high (in an attic, for example) and as far away from other objects as possible

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Old 11-10-2013, 6:10 PM
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Mike, thanks for everything so far but I am not familiar with the formula for making each leg of the dipole. I am doing the one with the tv balun.
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Old 11-10-2013, 6:47 PM
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As I noted in my message, the standard dipole frequency is;

234 / Freq (Mhz)

so divide 234 by 40 and you're going to come up with each leg being almost 6 foot in length. That should be easy to construct using the wire dipole idea that's in that OFCD article. Keeps everything cheap and KISS

Don't forget to keep that coax at a nice sharp angle away from the antenna - don't let it just droop down.

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Old 11-10-2013, 6:49 PM
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The only place I have to mount this antenna is in my attic. Does the antenna have to be completly vertical? Can I bend the legs in directions to get it to fit in my attic as long as I try to make it as vertical as possible.
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Old 11-11-2013, 2:01 AM
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Default Bending vertical antenna

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The only place I have to mount this antenna is in my attic. Does the antenna have to be completly vertical? Can I bend the legs in directions to get it to fit in my attic as long as I try to make it as vertical as possible.
If u remember some of the cheaper mobile antennas used like on 39.50 Mhz going down the road at 60 MPH were not very vertical but they still worked just a little more reflected power but receiving do what u can and you will be fine. The Motorolas we put on even bent some they were somewhat stiffer but worked in all my years of servicing radios i never got a write up for poor reception sue toi a bending antenna
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