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LPFM Antenna Recommendations

Posted: Wed Oct 04, 2017 9:16 am
by Slab Bulkhead
An LP I take care of recently had the antenna mounting scheme changed to get some separation between the bays and the tower face. In the course of this, the bays were lowered to the ground and I had a chance to inspect them after ~4 years out in the elements.

The antenna is an ERI 100A model. One bay had a cracked copper tip (water infiltration I presume) and the other also had water inside somewhere, not sure if it was in the boom or one of the arms but I was told it was sprinkling on the way down. An analyzer sweep makes me think it was inside the boom and possibly contaminated the pigtail cable. I discussed this with ERI and was told that there isn't really any waterproofing to the joints on the cross arms. I suspect if water got into the one boom it was the bottom bay and the riggers didn't leave enough of a drip loop in the pigtail.

Anyway, long story short, this one was sent back up but they are planning to replace it in the not too distant future. Does anyone here have any recommendations for replacement options if I wanted to put up something other than the 100A?

Re: LPFM Antenna Recommendations

Posted: Wed Oct 04, 2017 4:20 pm
by Lee_Wheeler
What frequency is it? If it is mid-band you can put up a cheap Nicom BKG77 and it will do just about as well as the ERI 100A. The design between the two isn't terribly different except that I think ERI tunes them to frequency before they ship.

My translator clients split about 50/50 between the Nicom and the ERI LPX series. The LPX antennas are way more expensive than the 100A but they are a sealed antenna. Given that they ship tuned they also work much better at the ends of the dial than the Nicom.

I have also put a couple of dozen of the Shively 6812 antennas that have been trouble free for a dozen years or so.

...Lee

Re: LPFM Antenna Recommendations

Posted: Wed Oct 04, 2017 4:23 pm
by NECRAT
ERI LPX series.

The Nicoms have issues with water penetration as well. Stay away from the "budget brands" like OMB, PSI, etc.

Jampro and Shively make good antennas, but ERI rototiller series is the top shelf. And it's your antenna, the final point before the listeners.

Re: LPFM Antenna Recommendations

Posted: Wed Oct 04, 2017 6:37 pm
by Deep Thought
Two antennas, same site, same transmitter models, same transmission line type and lengths, frequencies are about 2.5 MHz apart:

ERI 100A: VSWR is 1.06
Nicom BKG77: 1.32

Both are "out of the box" installations.

I really don't have an issue with the Nicoms but you'll want to consider how much it will cost to repair/replace it later. The ERI will probably last twice as long.

Re: LPFM Antenna Recommendations

Posted: Wed Oct 04, 2017 6:51 pm
by kkiddkkidd
I have been using NICOM BKG77 antenna's for the last few years for translators due to their broadbanded nature. I don't particularly like them but they seem to have good coverage and when a translator is bumped off it's freq, doesn't require a climb and retune. As of yet, I haven't had a BKG77 fail but have had a couple of the little OMB low powers leak, freeze and split along the feed section of the antenna.

If it is a situation where the freq can not be forcibly changed then I would definitely use a higher quality "tuned" antenna like the ERI 100a. If it is a translator that can be bumped, I would use a broadbanded antenna like the BKG77 to minimize tower climbs and retuning.

Regards,

Re: LPFM Antenna Recommendations

Posted: Thu Oct 05, 2017 9:01 am
by Slab Bulkhead
Interesting to hear that some folks are using the LPX series on translators. It seems like overkill for the power level, but I do like the idea of a sealed antenna. Does it need to be pressurized?

This station is near the middle of the band at 97.3, so a "broadband" antenna would probably work. However, I'd put the odds of a frequency change without needing a site change to go with it to be low, so a tuned antenna would be okay too.
Deep Thought wrote:
Wed Oct 04, 2017 6:37 pm
Two antennas, same site, same transmitter models, same transmission line type and lengths, frequencies are about 2.5 MHz apart:

ERI 100A: VSWR is 1.06
Nicom BKG77: 1.32

Both are "out of the box" installations.

I really don't have an issue with the Nicoms but you'll want to consider how much it will cost to repair/replace it later. The ERI will probably last twice as long.
The cost of the tower crew definitely outstrips the antenna price, so you definitely have a point there.

Re: LPFM Antenna Recommendations

Posted: Fri Oct 06, 2017 7:02 am
by TPT
Look at the SWR FM/1. Handles 500 watts, stainless steel for the most part. I've used a number for translators

Re: LPFM Antenna Recommendations

Posted: Fri Oct 06, 2017 8:01 am
by Lee_Wheeler
As far as pressurization, they can be but I usually don't bother. On the installations where there is nitrogen or a dehydrator there anyway I have used the air dielectric connectors (gas barrier and gas pass) and the pressure makes its way to the antenna through the hollow center conductor.

...Lee

Re: LPFM Antenna Recommendations

Posted: Tue Oct 10, 2017 10:50 pm
by The Wattcher
Jampro JLLP ......plays good for me

Re: LPFM Antenna Recommendations

Posted: Fri Oct 13, 2017 7:35 am
by Slab Bulkhead
I called ERI with a few questions on the 100A and did learn a good tidbit that I thought might be worth sharing.

If you do get a cracked tip due to water, lightning, or whatever, here's the replacement.
https://www.menards.com/main/plumbing/r ... 04&ipos=10