• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

Smallest fm transmission antenna

T

thejuggler

I'm looking to locate a small discreet fm transmission antenna for a low power set up (<25 watts)
We currently use a vertical half wave from NRG kits.
http://www.nrgkits.co.uk/cart_new/contents/media/l_hwv.jpg

However after a few months it is beginning to rust so we need a small lightweight durable replacement

Is there such a thing as a small stealth antenna that will give good results? The pole which supports the our half wave will not support a heavy antenna.

Pattern needs to be omnidirectional with an emphasis on focusing power on the horizon rather than directly below as we have had tvi problems in the past.

Any ideas?
 
The Comet is discreet, but relatively narrow band.

Don't tune it on the ground and expect it to be right at the top of the pole.
You pretty much have to tune it in place.

I also noted some heating even with only a 10 watt translator.
 
You should have ideally a 5/8 wave antenna. A half wave antenna is still good. If the antenna length is too small, the SWR will be very high. It may not damage the TX with 2 watts, but you might blow the output stage of your transmitter with as little as 20 watts! What station is this antenna for anyway? How much weight will the pole support?
And why would you care about TV interference directly below the antenna?
 
The pole will support a couple of pounds. To be honest my main aim is to make the antenna as inconspicuous as possible to avoid complaints - people are very wary of cell phone and transmission masts in my area. The antenna is in urban area so there are tv reception antenna in the vicinity hence the need to avoid tvi below my antenna.

I am looking at a 5/8 at the following link
http://www.aareff.com/5-8ant.htm
Seems like my best bet

how much clearence would the antenna need to have above the surrounding buildings and tv antenna to avoid causing interference? Would the length of the antenna be enough?
 
Have used the SWR CP antenna for a couple of translators with success. Very lightweight, < 10 pounds,but ruggedly built. Perhaps expensive for your use, last one I bought was $425.

The trade-off as you have found out, on many of these low-cost, lightweight LPFM antennas is that they are not very durable. After a few months in the wind and rain, they detune, or even fall apart.
 
This sounds suspiciously like you are putting together a pirate operation. What is your FCC callsign?
 
Doesn't Shively (sp?) make a small, low power antenna that is about 16" square, and you can stack them. Seems to me it's good for about 500 watts.
 
Then what is your callsign in whatever country you are licensed? You still sound like a pirate.
 
The Shively 6812 is probably the lightest CP antenna on the market, but the gain of a single 6812 bay will be 3 dB less than a vertical dipole or groundplane because it radiates about half its input power in the horizontal polarization.

I'm also curious to know where you're located. In fact, some countries do allow LPFM stations to operate with far less governmental control than here in the US. For example, New Zealand allows 500 mW EIRP at the bottom and top edges of the band, provided that the operator holds a "General User Radio License" (similar to an amateur license) and the applicable music licenses:

http://www.geocities.com/CapeCanaveral/9885/micronz.html

http://www.themulcher.co.nz/tech-is-it-legal.html
 
I don't believe he's overseas. I think he's a pirate operating in the US and we are in here giving him friggin' advice!
 
Let him have fun for what little time he will have. Anyone should be able to DF and report him in less then 1 hour. It will prove to be a big waste of money and time.

You can't hide from the DF meter! I always enjoyed the challenge to see how fast I could get to the site.
 
kyscott said:
I don't believe he's overseas. I think he's a pirate operating in the US and we are in here giving him friggin' advice!
Click to expand...

I do believe the gentlemen in question is located in Ireland. Which is not the US.
 
Michael said:
kyscott said:
I don't believe he's overseas. I think he's a pirate operating in the US and we are in here giving him friggin' advice!
Click to expand...

I do believe the gentlemen in question is located in Ireland. Which is not the US.
Click to expand...

The fact that he used the term "transmission mast" supports the idea that he is likely someplace where they use the "Queen's English". However the fact that he is concerned about being seen and distances from TV antennas says probable pirate.

My question is to everyone, who on here at some point in their lives has not put a little RF energy into the ether without the proper authority?

How about cranking the box a little past the specs once in a while to see what it could do?
 
what we need to remember is, a resonant antenna works both ways. While none of us would EVER do anything contrary to law or the FCC Rules, I can state with some experience, you can drive an FM turnstile with several hundred Watts before it gets so hot someting loses connection. It's actually harder to find a 50 - 300 Ohm transformer which will hold that power than it is to find an antenna which will. A homemade balun seems to work well though.
 
Michael said:
kyscott said:
I don't believe he's overseas. I think he's a pirate operating in the US and we are in here giving him friggin' advice!
Click to expand...
I do believe the gentlemen in question is located in Ireland. Which is not the US.
Click to expand...

Then let the gentleman speak up and remove doubt. Let the record reflect that he has been suspiciously absent since I brought up the possibility he is an unlicensed operator.

Licensed operators do not worry about TVI since they have already taken that into account when choosing a site. Visibility is also not an issue for a licensed operator since in most cases, transmitters and antennas are located in a place where visibility of the antenna is not an issue.
 
kyscott said:
Michael said:
kyscott said:
I don't believe he's overseas. I think he's a pirate operating in the US and we are in here giving him friggin' advice!
Click to expand...
I do believe the gentlemen in question is located in Ireland. Which is not the US.
Click to expand...

Then let the gentleman speak up and remove doubt. Let the record reflect that he has been suspiciously absent since I brought up the possibility he is an unlicensed operator.

Licensed operators do not worry about TVI since they have already taken that into account when choosing a site. Visibility is also not an issue for a licensed operator since in most cases, transmitters and antennas are located in a place where visibility of the antenna is not an issue.
Click to expand...

The "magic box" (do it wrong and you burn up your transmitter) below two 300-ohm 5 element FM antennas worked quite well 35 years ago to match 50 ohm coax to the two properly spaces beams. 300 watts into the array gave a bodacious signal across the intended coverage area 15 miles away from the studio site that was out in the country. You folks in the know do the ERP calculation. Bandwidth didn't matter with mono. The chosen frequency was that of a "B" that had been dark for a number of years.
I don't imagine the authorities (anywhere) have much of a sense of humor these days.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom