VHF-770mHz antenna recommendations?

[Cardiac69]

I have scoured the forums here and Googled the subject without finding much of an answer. I am trying to monitor a P25 TDMA (Phase II) system that is located at 771-774 mHz. I would also like to monitor the upper 150mHz range also. The P25 system is about 25 miles away and the VHF is within 10 miles. I am able to mount the antenna about 30 feet off of the ground. How would something like the Diamond D-130J perform at 772mHz?

Any other antenna suggestions? I really can only mount 1 antenna, so a yagi for 770mHz is not feasable.

Bob

 

[Fast1eddie]

700 Antenna

Hey Bob,

Interesting and a thought provoking post. Apartment dweller for now, I have a D130 30' agl with a run on .25 inch hardline. I'm outside of Pittsburgh and Pennsylvania now has 700 capability with every state agency assigned a talk group. Need to come up to speed with the specifics on that, was a two way radio tech years back.

Obviously a directional yagi aimed at the system will give superior results than a omni directional antenna, I think if the discone is placed high and clear feeding good quality feedline, then I would expect reception of some sort.

I have always been limited to mast height, but I ground my masts and am surprised with what I can hear dx wise when propagation is good. I live outside of Pittsburgh and routinely monitored Philadelphia police when they were on 453.xx, which Pittsburg uses present day. Philly went to 800, uncertain if it is monitorable.

Pretty good haul considering the Alleghenies block weather patterns and what not.

What is your receiver????

Let me know howyou make out.

ed

 

[JamesO]

700 MHz system Phase 2 system at 25 miles might be tough under the best of circumstances. Something to consider - https://forums.radioreference.com/s...mp-10-off-december-other-useful-rx-items.html

 

[Cardiac69]

Fast1Eddie, I am using a BCD536. I am using the stock antenna that came with it and cannot hear the PII system at all. When I take it to work with me (3 miles from a simulcast site), it performs beautifully. Soen't help me at home, lol.

JamesO, I am afraid that I just might have to build a yagi for 700mHz and put another antenna up some where else for VHF...

 

[iMONITOR]

I have scoured the forums here and Googled the subject without finding much of an answer. I am trying to monitor a P25 TDMA (Phase II) system that is located at 771-774 mHz. I would also like to monitor the upper 150mHz range also. The P25 system is about 25 miles away and the VHF is within 10 miles. I am able to mount the antenna about 30 feet off of the ground. How would something like the Diamond D-130J perform at 772mHz?

Any other antenna suggestions? I really can only mount 1 antenna, so a yagi for 770mHz is not feasable.

Bob

I've considered this antenna myself. Some on RR do not feel it would perform well, but I don't recall why.

Diamond D220R
https://www.universal-radio.com/catalog/scanants/6725.html

 

[JamesO]

JamesO, I am afraid that I just might have to build a yagi for 700mHz and put another antenna up some where else for VHF...

What you do not realize is with a proper LNA that has a low enough noise figure, signals can be pulled in with quite good results. So for example you are thinking you must have a 700 MHz Yagi when in fact you might be able to use a decent outside omni antenna with a high quality, very low noise figure LNA and be able to receive the system you cannot hear.

You can use regular RG6 CATV coax and put the money into the LNA, you could even use a very cheap antenna in many cases and still have good results.

The only down side of an LNA is if you have very strong signals in your area that would compress and/or cause intermods in the LNA. I had to use a FM Notch filter because I am 3-5 miles to 3 very high power FM broadcast towers, but after buying and trying 6 different FM notch filters and 6 different LNA's I found this combination works very well and I can now hear many of the adjacent systems that I could not have heard otherwise, even with the antenna I have set up now.

IMHO and experience people miss the big picture and focus on the wrong way to pull in signals. While the LNA configuration may not work in all installations and for all services, I have also had a lot of people claim this will not work under most conditions, which is not the situation in my case. I am 2 miles from Washington, DC and under 8 miles to almost all the FM and TV transmitters for my market and have a number of cell phone towers within 1 mile and I have very little, if any artifacts or problems due to the high level and quantity of signals.

This set up is something to consider, you might be surprised on how it performs but at the same time you may have some fine tuning or other things that challenge the ability to use this set up in your location. I am in a major Metro area that is an RF rich and RF challenging environment and I have very good results with this configuration. I hear things I would not have otherwise been able to monitor.

 

[KD4UXQ]

You can make dipoles out of many items such as aluminum rods possibly taken from old TV antennas, or brass welding rods or anything you can fashion a rigid element out of. Multiband vertical dipoles work very well and I have made several of them. Just slant the elements into the shape of a V on the top element and the bottom element, and cut the elements for the center frequency of the range of frequencies for each band you want to monitor. Both upper elements would be tied together and connected to the coax center, and both lower elements would be tied together and connected to the coax shield. You would not want to go beyond 45 degrees so that you are not approaching a horizontal polarized antenna configuration. And you want a reasonable amount of separation of the elements on each half of the dipole.

PVC pipe is an excellent mount for the elements and you can usually find an easy way to mount the elements to the pipe with stainless steel screws. Either holes in hollow rods, or small gauge rods bent into a loop on one end to mount with a screw.

 

[Cardiac69]

This gives me some options. I wonder how a cheaper discone such as the Tram 1410 would do in conjunction with an amp such as what JamesO suggests above? What concerns me is the specs say there is a gap between 470 and 900 mHz.... I want to figure this out before the harsh winter weather sets in here in NW Indiana. Thank you for all of the ideas....

Bob (K9YH)

https://www.amazon.com/Tram-1410-Di...8&qid=1507630265&sr=8-3&keywords=tram+discone

 

[Ubbe]

It's a discone antenna that covers the whole range, no gaps. Google the antenna and check other sources. Sometimes you see some frequency ranges being mentioned together with a discone but often it is the transmit frequencies allowed to be used by radio amatuers and the free public channels as CB radios and FRMs dot radios and such.

Don't take notice of anything than the lowest and the highest frequency specified. The lowest frequency is given by the lenght of the lower elements and the highest by the construction of the "crown".

The lower elements are 32 inches and the calculator says it's lowest frequency is 100MHz and below that it degrades rapidly. https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/ (use the radials lenght)

/Ubbe

 

[paulears]

What you need to do is research the data for these kinds of antennas on a graph, because while saying there are no gaps is true, there are dips of many dBs and you don't want your wanted frequency in one of the dips, as the best performance is no gain, and the worst, a few dB down on that. Maybe a log periodic pointed that way could work, but really you are going to have to shell out the money and take a gamble.

 

[JamesO]

In general, unless an antenna has a fair amount of gain in a specific band, most antennas are pretty wideband. For example most Discones are fairly wideband on receive. The only thing I do not like about discones is they tend to have a higher angle of radiation due to their design. They tend to do a good job for aircraft in the sky, but I prefer something much different for my antenna configurations.

Since the Antennacraft ST-2 scanner antenna is no longer available, I would consider antennas like these.

The Procomm Spider is not as good on VHF due to its size, but for the money it seems to be a decent option especially if you are trying an attic mounted antenna and are limited on space. Procomm Spider Police scanner home base station antenna w/ 50ft coax cable | eBay

The DPD Productions Omni X is a good antenna but is more expensive and a rather large antenna. Due to the element length it is good for VHF coverage DPD Productions - Base & Mobile Antennas for Radio Scanners: VHF, UHF, NOAA, Low-Band, 700 MHz, Police, Fire, Public Safety

Another option is Ed Fong TBJ-1 antenna. I have not tired this yet, but for a sturdy omni antenna that does not take up space, I would consider this as a possible option. I plan on testing one of these out in the next few months as a wideband Scanner antenna.
Ed's Antennas - Home

I would consider the LNA configuration with one of the above antenna options over a discone. I think one of the first 2 antennas would be a good option depending on the space and installation options available.

 

[Cardiac69]

Thanks folks for more great ideas. Ubbe, I should have known better on the gaps being pretty much for the transmit side.

I will take a look at the antennas above. Not really pressed for space so I do not have to go with a compact size..

Bob

 

[JamesO]

For example, you could go with the ProComm Spyder antenna and the LNA configuration for the price of the Omin-X antenna. The ProComm comes with coax, you would just need adapters to get the LNA to the PL-259 connector on the antenna and then decide if you want to stay with the PL-259 on the coax side.

This is a smaller antenna to start with, but may give you the results you are looking for. Often with a decent LNA you could almost use a coat hanger for an antenna.

Only item to watch out for on the ProComm Spyder is how the lower elements slip into the antenna and they can short to the center conductor of you are not careful.

See this video for a discussion on how this can happen and what to do about it.- https://www.youtube.com/watch?v=1xzr4-l6mLU

 

[N9PBD]

You can also try this route:

The Larsen Tri-Band mobile antenna, NMO mount, mounted to a ground plane kit.

https://www.amazon.com/Larsen-NMO150-450-800-Tri-Band-Nmo-Antenna/dp/B00P9JAVF6

https://www.amazon.com/TRAM-1465-Mo...07730492&sr=8-2&keywords=nmo+ground+plane+kit

 

[JamesO]

Another better quality antenna to consider - Classic VHF UHF Base Station Antenna 25MHz

 

[Cardiac69]

More great ideas. Thank you!

 

[Cardiac69]

I picked up a Procomm Spider from a local ham and have it at 28' fed with RG-214. I can receive the 700mHz P25 Phase II system I was trying for, but it is a little garbled at times. Might try a pre-amp or going up another 10'.