Nicom BKG 77

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musiconradio.com
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Nicom BKG 77

Post by musiconradio.com » Sat Dec 24, 2016 9:38 am

Merry Christmas everyone!

We are looking to add a second Nicom BKG 77 bay to our system. This should increase our gain (and hopefully improve coverage), and decrease our TPO (power bill savings).

Is anyone using a several BKG 77's with a combiner?

How is it working for you?

Any installation suggestions that worked well for you?

Lee_Wheeler
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Re: Nicom BKG 77

Post by Lee_Wheeler » Sat Dec 24, 2016 12:53 pm

I assume this is for a translator or a LPFM.

I have several new translator builds in various stages of progress and the economies have always worked out to use a one bay with a bigger transmitter rather than to go to the added expense of a two bay. One factor that has never been part of the equation is the power bill but unless the power is stupid expensive the basic meter charge is more significant than the power itself.

The question for most of my clients is more between a real antenna like an ERI LPX1 or a "broadband" Nicom BKG 77. The actual dial position is part of that equation but one I finished earlier this year was at 98.1 MHz which the Nicom would have loved but the client wanted the best facility possible and we used the ERI and a TPO of a fuzz over 800 Watts. I have another one where we are putting up a Nicom further up the dial at around 105 MHz but it will still be a one bay because the price difference between a VS1 and a VS 300 was less than the cost difference between a one bay BKG 77 and a two bay version of the same antenna. Since you already have the upfront transmitter cost baked into the equation I'm trying to figure out what you will accomplish with a two bay.

I am not real sure that you can just add the second bay and the interbay harness and expect it to work since the existing one bay is a 50 Ohm antenna at the input and a two bay is set up to be 50 Ohms at the input to the harness which would dictate that the individual bays are not 50 Ohms unless there is some sort of strange transformer section in the harness.

One other factor is that you will need to re-file the Form 349 to get a new construction permit since the antenna is specified in the actual CP application and then you will need to file a new license application after the change is made. If you can do the paperwork yourself great but if you need to hire a consultant it will add a thousand bucks or so to the cost along with the FCC filing fees.

...Lee

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Re: Nicom BKG 77

Post by TPT » Sat Dec 24, 2016 2:14 pm

Details! How much TPO now? What kind of station? You can replace the antenna with a different antenna with more bays on an LPFM at any time--but the ERP must stay the same. See section 73.875 for details. A construction permit application is needed if you would be increasing ERP, and, of course, you can't exceed the maximum power for your antenna height above average. For translators, an application is needed before changes may be made, see Section 74.1261.

Another factor is the cost of a tower climber to change out the antenna.

musiconradio.com
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Re: Nicom BKG 77

Post by musiconradio.com » Sat Dec 24, 2016 2:27 pm

I am aware of the application modification. The question is simple. A single bay to a second bay (going from a -3b gain to a 0 gain), with a combiner. Will it improve coverage. Looking for comments or a case study. Thanks.

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Re: Nicom BKG 77

Post by TPT » Sat Dec 24, 2016 2:55 pm

Assuming no change in ERP, no, not to any noticeable degree. In fact, for a given antenna location, height, ERP, etc., the single bay may work a little better than the two bay configuration. Mostly for completely random reasons, e.g., inadvertent null created with a side-mount antenna on a fat tower, or differing close in radiation patterns between the single bay and two bay (which may have less radiation at lower angles).

Since a single bay Nicom is rated at a maximum of 2 kw, I assume your present ERP is fairly modest. The only way to have a significant increase in coverage is to increase the effective radiated power at your AHAAT, or raise the antenna (increase AHAAT). And with an ERP increase, the old rule of thumb applies: to double the coverage you need four times the power (ERP).

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Deep Thought
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Re: Nicom BKG 77

Post by Deep Thought » Sat Dec 24, 2016 4:43 pm

.
musiconradio.com wrote:I am aware of the application modification. The question is simple. A single bay to a second bay (going from a -3b gain to a 0 gain), with a combiner. Will it improve coverage. Looking for comments or a case study. Thanks.
The answer is simple, too: It will not do anything to improve coverage as the ERP and/or the HAAT won't increase. End of discussion
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

musiconradio.com
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Re: Nicom BKG 77

Post by musiconradio.com » Sat Dec 24, 2016 4:54 pm

Thanks everyone.

level42
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Re: Nicom BKG 77

Post by level42 » Sat Dec 24, 2016 8:16 pm

Damon, I can say from experience, having built over a hundred translators...the simple answer is: probably not.

Knowing a little more about the height, intended coverage area, etc...would help.

The single bay setup with higher TPO will almost always have a more omni pattern with less multipath and better building penetration. If you are trying to "squeeze" a signal to the horizon to cover a specific area a little farther away, a multi-bay setup will help with that.

You are not going to see any significant change in power bill between these two setups.

All of that being said, replacing the Nicom with a tuned antenna like the SWR FMEC-1 or the ERI 100A will give you a noticeable improvement in coverage over the Nicom. A broadband antenna is OK at all frequencies, but great at none. A tuned antenna is great at one frequency. In every case that I have replaced a Nicom with a tuned antenna, I've seen measurable improvement in coverage.

Hope all is well and Merry Christmas!

-Chris Hall
www.reelaudio.net

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kkiddkkidd
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Re: Nicom BKG 77

Post by kkiddkkidd » Sun Dec 25, 2016 9:36 am

There is a local station using an 8-bay BKG77 on a 6kw Class A. No I don't understand why either...
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Kevin C. Kidd CSRE/AMD
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Ryan Williams
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Re: Nicom BKG 77

Post by Ryan Williams » Thu Jan 05, 2017 8:31 pm

kkiddkkidd wrote:There is a local station using an 8-bay BKG77 on a 6kw Class A. No I don't understand why either...
Wow. I've never heard of such an extreme setup for that class. Is the signal as bad as one might expect?

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kkiddkkidd
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Re: Nicom BKG 77

Post by kkiddkkidd » Fri Jan 06, 2017 1:07 pm

It's really not that bad, but it definitely isn't as good as it was with the jampro four bay that was up there. They have had A and possibly two instances of bad jumpers and/or power dividers in less than a year.
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Kevin C. Kidd CSRE/AMD
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Shane
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Re: Nicom BKG 77

Post by Shane » Fri Jan 06, 2017 11:24 pm

$OUCH$
Mike Shane, CBRE
---Omaha---

Ray
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Re: Nicom BKG 77

Post by Ray » Mon Jan 09, 2017 7:29 am

I've heard several folks say that a narrow band slant vee antenna will provide a better signal than a broadband model like the BKG-77.

I was wondering if anyone knows why?

The radiating elements are very similar, basically same slant vee dipole construction. I would think the radiating pattern would be similar.

If the issue is in the balun/matching I would think the power would be very limited if it has more than a few tenths dB loss.

More complex matching networks usually involves more loss but high power and loss are not a good combination.

I have a BKG77 on the ground and have never tried to look inside the balun section. Does anyone know what the matching scheme for the BKG77 is?

It might be fun to do a A/B field strength comparison test.

Ray

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Shane
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Re: Nicom BKG 77

Post by Shane » Mon Jan 09, 2017 11:13 am

We have a translator that was using a Nicom BKG-77 and were quite happy with its performance.

I use past tense because we had to change it out for an antenna with more power capability to accommodate combining two translators into the one antenna. The new antenna is a Shively (6833, I believe) and we note no difference in coverage. Both antennas are broadband.
Mike Shane, CBRE
---Omaha---

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