2 Options for VHF/UHF antenna

[Rastaman147]

Hi all -

I'd like to get some opinions for 2 different antenna location setups I am considering:

The antenna would be something like this: CSB-750A COMET 146/446 MHz Dual-Band High Performance Mobile Antenna, Chrome, Gain: 3.6 / 6.1 dBi, Connector: PL-259 (UHF), Max Power: 150 Watts, Length: 42"

The radio would be a 2m / 70cm dual band, either a mobile or portable with 50 - 100 watts power being used as a base station from my basement.

For the antenna, I would like to know which of the following location will give me better results:

1. antenna mounted on the floor of my attic (about 10 feet above the ground). Would be almost directly above my rig using maybe 15 feet of coax (maybe 20 feet max, but probably closer to 12 - 15 feet.)

or

2. same antenna mounted outside on my antenna mast at the other end of my house, about 20 feet above the ground. The bottom of the ham antenna would be about 6 feet above the edge of my roof. This antenna would be sharing the mast with my sc-2 scantenna, and would be positioned at the same place vertically as the scantenna. There would be maybe 2 -3 feet between the 2 antennas. This would require about 90 -100 feet of coax. I can use RG8 coax for this, if necessary.

Is there a clear best way to go here?

I am in a suburban neighborhood in central Pennsylvania with lots of houses and 50 foot trees. The terrain is hilly, with mountains maybe 4 miles to the south and 15 miles to the north. I have no trouble hitting a 2m repeater and a 70cm repeater, both about 4 miles to the south, possibly located on the mountain using an HT on low power and a rubber duck from my basement, but I'd like to improve my range a little.

*** What I am trying to get a sense of here is the performance trade-off between short coax, indoors and lower mounting position vs longer coax, outdoors and a slightly higher mounting postion using the same antenna. If the outdoor option is significantly better, I'm sure a different type of antenna would improve the performance even more, and I would actually use whatever type gives the best results.

Thanks!

 

[n5ims]

I'll answer your main question first. Since VHF/UHF is generally "line of sight", you'll do much better with a higher antenna than a lower one. You'll need some quality low-loss cable, but you'll be much happier with the results.

Since the antenna you mention is a mobile antenna, not a base antenna, and you'll be installing it at your home in a more-or-less permanent type install, you really should move to a base type antenna. You'll get better results and end up with a much sturdier installation. There are several available from your selected store and manufacturer (from Comet GP1 Vertical Antenna through Comet GP9 Antenna). You'll probably end up with more gain and nearly certainly a better ground plain (aka counterpoise) which is often thought of as the "second half" of a vertical antenna.

Next you may want to think about mounting your ham antenna (where you'll be transmitting presumably) that close to your scanner antenna. With zero vertical separation and only a few feet of horizontal separation you could easily damage your scanner when you transmit. Try to separate them by 20 feet or so vertically (more if possible, a few feet less if you really must) to keep that transmit signal from frying your scanner's front end circuits.

Coax should be a major item, not something that is just easy to find. First off you want some quality coax, Belden, Times, or Andrew are generally good bets. Stay away from the cheap stuff since they may be very poor quality knock-offs. At the least, use some good quality RG-8 (not the thinner 8x, which is a totally different design). LMR-400 would be better. Andrew LDF4-50A would be much better (check for end-of-reel lots on eBay, local hamfests, etc.). See this thread (http://forums.radioreference.com/coax-cable-discussion/263871-coax-decision-wilson-vs-times.html) for information on why quality brand is the way to go since they discuss Times vs. Wilson brand LMR-400.

 

[mmckenna]

Good advice above ^^^

Here is a fun little tool to play with when considering the type and length of coax for your system:
Coax Calculator
You can enter the coax type, frequency, power, etc. and it will give you some useful info about how much signal you'll lose in your cable run. Put in 100 watts at 146MHz with RG-8, and you'll see that with RG-8, you'll lose almost half your signal in cable losses. Change it to LMR400, and you'll see cable loss drops to about a 1/3rd.
Keep in mind that cable loss works both ways. While it will reduce your transmit power, it'll also affect what you are receiving. Too much cable loss can result in a received signal being too weak once it reaches your radio to break squelch.

 

[popnokick]

I vote for the attic, away from the scanner antenna and a much shorter coax run. But plan to use a base antenna in your attic that does not require a ground plane, such as the half-wave coaxial "flower pot" antenna described here or a similar half-wave:
http://forums.radioreference.com/bu...761-half-wave-coaxial-flowerpot-vertical.html

 

[LtDoc]

If I had the choice, The antenna would be outdoors and as high as I could get it. An attic antenna is handicapped because of the roof, etc, being in the 'way' of the signals. How much attenuation that would be depends almost entirely on what the roof, etc, is made of, but there will be some attenuation.
I would also suggest using a 'base' antenna rather than a mobile antenna simply because they are typically 'complete', you don't have to furnish a 'groundplane'/counterpoise/'other half', and can have some gain to them.
Using a low loss feed line especially if it's a long run is a very good idea.
Lots of "if's and buts", and you will have to decide which would be most suitable for you.
Have fun.
- 'Doc

 

[ranger821]

Outside antenna with good low loss coax. Ditto on the the scanner antenna's. Keep them away from your ham antenna. I run a diamond X-200 at about 22 feet. Works great here on the coast. With the hilly terrain there in Pa., the antenna needs to be as high as possible and NOT in the attic.

Just my 2 cents worth.
KB4OIF

 

[popnokick]

Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 6_1_3 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/6.0 Mobile/10B329 Safari/8536.25)

One other idea.. If you're willing to compromise on the scanner, put the scanner antenna in the attic and move the 2M antenna up where the scanner antenna was... As high as you can get it, and with best quality coax. Ideally you could put a much taller mast on the far end if the roof and get major vertical separation between the two antennas on the same mast/tower. But based on your description I'm guessing that's not possible.

 

[Rastaman147]

Thank you all for your input!

This forum is really great! You folks have pretty much answered my question. It sounds like the benefit of having the antenna up higher will outweigh the problems of the long feedline, so I think I will get one of the base antennas that n5ims linked in his post, probably the GP-3, and mount it outside on my antenna mast using the LMR-400 or LDF4-50A coax.

Regarding the scanner antenna, if the only concern is damaging my scanner by transmitting on the 2m radio, then I should be ok, as I will not have both units operating at the same time. Also, it looks like the GP-3 base antenna is about 6 feet tall -- I should be able to extend my mast a little bit so the 2m antenna is higher than the scanner antenna as well.

Is it necessary / advisable for me to get an antenna tuner, or will I not need that for a 2m/70cm radio using a 2m/70cm base antenna?

 

[mmckenna]

This forum is really great! You folks have pretty much answered my question. It sounds like the benefit of having the antenna up higher will outweigh the problems of the long feedline, so I think I will get one of the base antennas that n5ims linked in his post, probably the GP-3, and mount it outside on my antenna mast using the LMR-400 or LDF4-50A coax.

Don't overlook LMR-600. Good cable, and a bit cheaper than the Heliax.

Regarding the scanner antenna, if the only concern is damaging my scanner by transmitting on the 2m radio, then I should be ok, as I will not have both units operating at the same time.

Doesn't matter. Turning your scanner off doesn't disconnect the antenna. Even with the scanner turned off, if the antennas are too close, you WILL damage the scanner. The only way to solve this would be to disconnect the antenna, either by disconnecting from the back of the scanner, or installing a switch. But, forget to disconnect it or switch it, and you'll toast your scanner.

Also, it looks like the GP-3 base antenna is about 6 feet tall -- I should be able to extend my mast a little bit so the 2m antenna is higher than the scanner antenna as well.

Unless you set them up so there is enough vertical separation (NO Overlap) between the antennas, it doesn't fix the issue.

Is it necessary / advisable for me to get an antenna tuner, or will I not need that for a 2m/70cm radio using a 2m/70cm base antenna?

Not necessary. You should check the final installation with a directional wattmeter/SWR meter. If the GP3 is a dual band antenna, that is all you need. The antennas are usually broad enough to cover the whole band without tuning it. If it isn't, look for a better antenna.

 

[AgentCOPP1]

If you're using VHF/UHF, I would highly recommend trying to get a different connector other than the PL-259. Those don't work so well in UHF even though they're named UHF. They can cause a lot of standing waves in your feed line which can harm your radio. I'm thinking you might want to look at BNC or TNC.

 

[prcguy]

What? UHF connectors are a tiny bit lossy at UHF but we're talking a tenth of a dB or so and its not going to harm your radio. Motorola supplied UHF connectors on their commercial UHF repeater duplexers for many years and thats a fairly critical use compared to hamster use. N is better but UHF is very useable through 500MHz.
prcguy

If you're using VHF/UHF, I would highly recommend trying to get a different connector other than the PL-259. Those don't work so well in UHF even though they're named UHF. They can cause a lot of standing waves in your feed line which can harm your radio. I'm thinking you might want to look at BNC or TNC.

 

[AgentCOPP1]

What? UHF connectors are a tiny bit lossy at UHF but we're talking a tenth of a dB or so and its not going to harm your radio. Motorola supplied UHF connectors on their commercial UHF repeater duplexers for many years and thats a fairly critical use compared to hamster use. N is better but UHF is very useable through 500MHz.
prcguy

You're right, it's definitely usable, but if you really want the best performance possible out of your radio, it's better to stay away for the UHF connectors for the UHF band. I shouldn't have said that it can damage your radio necessarily, but it's certainly not ideal. It's more of a stickler thing because technically the UHF connectors are in no way superior to other types, and some people would really rather have the best installation possible, but it's entirely up to you. It also depends on the quality of the connector and what materials are used, but I'm just one of those people that would rather have the best installation possible.

 

[Rastaman147]

UHF connectors / Update on antenna

Funny that you mentioned that today, because I was planning to come here to update you folks on my current antenna situation, and I had planned to mention the difficulty I am having wrapping my mind around the whole antenna / cable / connector impedance match / signal loss thing.

I am new to scanners and ham radio, and one thing that I can say for certain so far is that I really like BNC connectors and I really dislike the PL-259, SMA, and reverse SMA. So I am thinking as I progress in this hobby, every project I take on is going to involve making it work with a BNC connector.

For my permanent solution, I've decided to go with the outdoor installation with a base antenna and the best coax I can afford, but it will take me a while to save enough $$ for that, so for the meantime, I built the flower pot antenna linked by Popnokick (THANKS FOR THE TIP!!!), mounted in my attic with some RG-6 coax I already had, and it's awesome! Works much, much, much better than the rubber duck or the 15" dual band antenna.

With the flower pot design, the antenna and feedline are the same piece of coax, so it was easy to just terminate it with a twist-on BNC connector from Radio Shack, but I must have spent at least 6 or 7 hours researching connectors, and I can see that it's going to take A LOT more research before I know what I'm doing with connectors. Many of the antennas have the SO-239, so it looks like I will be limited to PL-259 (on the antenna side, at least) right out of the gate.

And it also looks like soldering is the only good way to attach the connectors. I watched 3 or 4 videos, and checked out a few step-by-step guides, and it looks like it's way beyond my ability. I am terrible at soldering, too, so I guess at some point I'm just going to have to buy a bunch of connectors, a couple rolls of solder, and practice making patch cables or something, but I'm not looking forward to it.

Anyway, thanks again for all the advice. I'm learning, but it seems like the more you learn, there more there is to learn!

 

[AgentCOPP1]

@Rastaman

I don't understand how some antennas can ONLY have SO-239. Most of the antennas I've seen give you multiple options for different connectors. Could you give me a link to the specific one that you want, perhaps?

Soldering is a bit difficult to learn and it takes a lot of practice. However, if you devote the time, maybe 10 minutes a day, to practicing soldering cables together, you can get very proficient at it very quickly. When you get the idea of it, it's actually not as complex as it may seem at first. Of course it depends on what you're trying to do, but most cables are pretty easy to solder. You'll also need to make sure that you have a high-voltage soldering gun if you're working with coax. If you buy the wrong one that's meant for more surface-mount soldering, you can end up frustrating yourself since the SM soldering guns can't heat up the solder enough to get it to melt through your 12 or 10 gauge wire, or whatever the hell the equivalent RG is for coax. That's something I've learned the hard way haha, so be sure you know what kind of gun to get before you get discouraged.

 

[Rastaman147]

Here's the base antenna I was considering: Comet GP1 Vertical Antenna

This is a mobile I was looking at: https://www.hamcity.com/store/pc/CA-2X4SR-p212.htm

I didn't mean to say I wasn't able to find an antenna without the SO-239 -- Only that it seems to be the most common. Since the performance is inferior to other connectors, and since it's such a pain to connect, especially to a scanner or HT, I was just kind of puzzled as to why the antenna companies use them at all.

Is it better to use a soldering gun? Or can I use an iron? The videos I watched showed soldering guns, but they look kind of bulky and difficult to use around something as small as a coax connector. If you needed to buy a soldering gun or iron, which one would you get?

Thanks again!

 

[LtDoc]

The GP-1 antenna is okay, don't expect exceptional performance, it just doesn't have it. As for the CA-2X4SR mobile antenna, it is well worth it if you have need of an antenna that's capable of use in the 150 Mhz ranges. It's made with both the 'M' or SO-239 connector and an NMO type connection/mount. Just depends on if the dealer you are dealing with carries both types.
Having used the GP-1 before, I wouldn't recommend it over a common 'J'-pole, they both perform about the same.
- 'Doc

 

[dksac2]

Get a UV-300 OPEC antenna. You can get them for $100.00 At that price, it is the same as another brand that is for the most part the same antenna at 1/2 the price.
It has 8.3 DBI gain on VHF and 11.7 at UHF frequencies.
Use some LMR 400 coax and get the antenna up as high as you can. This is one case where the extra height will not hurt you because you will gain more from the height than loss from the extra coax.

As to the scanner antenna, move it or put it in the attic. If possible, use "N" connectors as they work best at UHF freqs.

I talk more than 50 miles with my OPEC antenna at 40 feet up.
Before the Opek antenna, I had a Diamond 300 antenna with 6.5 dbi gain, same coax and height. There was a major difference going to the opec antenna. I could hit repeaters that I could not even break the squeltch with using the Dimond. The OPEC is the best deal going and flat out talks and hears.

John

 

[AK9R]

I believe you are referring to an Opek UVS-300. Note the spelling of Opek.

UVS-300 ( VHF/UHF ) DUAL BAND BASE STATION | Welcome to OPEK

I'm also finding Opek antennas under the Workman brand name.

 

[dksac2]

If you're using VHF/UHF, I would highly recommend trying to get a different connector other than the PL-259. Those don't work so well in UHF even though they're named UHF. They can cause a lot of standing waves in your feed line which can harm your radio. I'm thinking you might want to look at BNC or TNC.

You want to use "N" connectors. They are waterproof, good to 3 gigs or better and a much better connector than the small one's mentioned. L-Com has real Times LMR 400 for 75 cents a foot, I've used nothing else, works great. Get that antenna up as high as you can.
Also check out the OPEK VU-300 antenna. 8.3 gain at 2m and 11.7 at 70CM. I have one and it talks further than anything besides a beam.
I can't remember if the OPEK comes with an "N" connector, if not, the Diamond 510 does and has the same specs as the OPEK, just twice as expensive.

If your going to use a mobile antenna, the CA 2X4 is a fantastic antenna. I have one on my truck. It is very wide banded. The SWR on 2 Meter is 1.2 to 1, just as good on 70CM and well under 2 to 1 on GMRS. I think it's the best mobile antenna going. It has more gain than 95% of the mobile antennas out there. Don't skimp on the antenna, spend the money and get the best you can afford, same goes for coax. You can have the best radio in the world and a cheaper antenna and it will not talk far at all, the antenna and coax make the radio.

John

 

[AC2OY]

Great find guys I wonder how much their multiple band antenna goes for?