VHF High base antenna

[nick1427d]

Looking for some opinions on what might work best for what I'm trying to achieve.

I'm slowly but surely buying the necessary items for getting my antennas out and up. I will be focusing most of my attention at this point to vhf High (150-160). This antenna will be about 50' up. I live in sort of a valley I guess. Most of the agencies I monitor now can be heard with nothing but a back of set antenna. However with everyone in my area going P25 and 800mhz I was interested in seeing if I could "pull in" some of the more distant stations that don't have plans on switching. These would be roughly 20-30 miles out. I can get them now with a simple 1/4 wave i have on my guttering just very scratchy. This antenna will be on a multicoupler going to multiple scanners. I have plans to obtain high quality coax for my main feedline, so hopefully everything will have minimal loss.

My question;

What do you guys recommend for a good all around omni?

I guess I'm still confused on wavelengths and how the correspond to receiving. I know how wavelengths relate to transmitting just wondering too if this is the same for receiving?

Note that I'm NOT willing to spend hundreds of dollars for an antenna that I'm not transmitting on.

thanks in advance

 

[n5ims]

I guess I'm still confused on wavelengths and how the correspond to receiving. I know how wavelengths relate to transmitting just wondering too if this is the same for receiving?

A tuned antenna is a tuned antenna, transmit or receive, it will work better than an antenna that's not tuned for the desired frequency range. While it's more important for the antenna be properly tuned when you transmit (you could burn out the final output transistors if the antenna is too far out of tune), it's also important when you receive (although no damage will be done to the radio, you'll end up with less signal).

I have plans to obtain high quality coax for my main feedline, so hopefully everything will have minimal loss.

Quality low loss coax is important since a great antenna's signal can be totally wiped out using the wrong coax.

What do you guys recommend for a good all around omni?

Start by looking for a single band (or dual band that covers your desired frequency range). Compare the gain numbers and look for those that have the highest numbers. One note on this is that there are two different ways companies report the gain numbers and they are not the same. Always assume that they're reported in dBi units unless they specifically say dBd. When comparing two antennas, one reported in dBd and the other in dBi (or not indicating what units they report their gain in), simply add 2.15 to the dBd numbers and you have an apples to apples comparison. If you're comparing dual band antennas, make sure you use the numbers for the same band in your comparisons! If you compare a dual band VHF-Hi/UHF antenna with gain numbers of 3/4.5 dBd to a single band VHF-Hi antenna with a gain number of 4.75 (no indication of which type of units are being reported), you should end up with a comparison of 5.15 dBi for the dual band and 4.75 dBi for the single band antenna (the dual band will win out here).

Generally ignore those wide band antennas, such as a discone since they'll have quite low gain values (generally 0 dBd or 2.15 dBi of gain). What you get in frequency coverage, you'll pay for in gain (or lack there of).

 

[nick1427d]

So say a 6 db (not dbi) would be a good all around omni for my app?

Like this:

Tram 1490 - $89.95 : The Antenna Farm, Your two way radio source

or:

Tram 1491 - $99.95 : The Antenna Farm, Your two way radio source

 

[prcguy]

Assuming mfrs are using dBi gain over dBd in advertising is only part of the problem as may mfrs just make up numbers. I would be surprised if the Tram antennas in the links are rated that much gain even in dBi. They are also fairly narrow band so if you tune them for 155Mhz they will be down slightly at 150 and 160Mhz.
prcguy

So say a 6 db (not dbi) would be a good all around omni for my app?

Like this:

Tram 1490 - $89.95 : The Antenna Farm, Your two way radio source

or:

Tram 1491 - $99.95 : The Antenna Farm, Your two way radio source

 

[krokus]

Generally ignore those wide band antennas, such as a discone since they'll have quite low gain values (generally 0 dBd or 2.15 dBi of gain). What you get in frequency coverage, you'll pay for in gain (or lack there of).

The lack of gain might not be a bad thing. The additional height might give sufficient clarity of the desired signal. If there are strong transmitters nearby, a gain antenna could cause desense or front-end overload.

 

[krokus]

Most 1/4 wave antennas, tuned for the center of the target frequencies, should work well.

 

[nick1427d]

The lack of gain might not be a bad thing. The additional height might give sufficient clarity of the desired signal. If there are strong transmitters nearby, a gain antenna could cause desense or front-end overload.

I guess I should note that I will be having a 1/4 wave nmo ground plane as well connected to a number of separate scanners for local.

 

[Avery93]

For an inexpensive VHF omni, I can recommend the DPD Outdoor Vertical. I've had one up for almost 4 years and it has held up great. If you order one built to 155 MHz, it will cover 150 to 160 MHz receive only with no problem. It claims 3 dBi gain (0.85 dBd), and I would say that's fairly accurate.

If need something with more gain, you might look into the Laird FG1523. Several agencies in my area use these, and except for the narrow transmit bandwidth, they seem to be good antennas for the price. For receive only use, it should still cover 150 to 160 MHz just fine, and it's rated at 3 dBd (5.15 dBi) gain.

A local fire department bought one of those Tram 1490 antennas, and while it works okay, I am not sold on it's durability, especially regarding water intrusion. Also be aware that the claimed "6.7 dB" gain is nowhere close to accurate. I would say it's around 3 dBd tops.

 

[nick1427d]

Thanks for the help guys. Another question;

Would there be much difference (benefit) in a "more expensive" 5/8 wave true base antenna as opposed to me putting a 5/8 wave nmo whip on a nmo ground plane?

I figure durability and wind tolerance might be a problem long term?

 

[Rt169Radio]

Thanks for the help guys. Another question;

Would there be much difference (benefit) in a "more expensive" 5/8 wave true base antenna as opposed to me putting a 5/8 wave nmo whip on a nmo ground plane?

I figure durability and wind tolerance might be a problem long term?

I have a Larsen NMO base ground plane whip antenna setup that has been up for quite a while, and it hasn't given me any problems. But if you have the funds and want too, I would go with a "real" base antenna.

 

[dksac2]

The antennas you mentioned will give you more gain than the others, all antennas for VHF/UHF seem to be rated in DBI, not DBD, so the highest dbi antenna will have the most gain. I use a different named antenna than the Tram, but it's the same antenna and it has fantastic range and ears, the base is at 35 feet and I too live in a valley. You can figure the tram antenna will give you a little over 3 DBD gain, so it will double the output of your radio, but you must use LMR 400 coax, especially at 800 MHz and keep the run as short as possible, there is a lot of signal loss in coax at VHF and a great deal more loss in the 800 MHz range. You will find 1/4 wave antenna to have negative gain by the time you get the signal through the coax, so you want as much gain as possible from your antenna. The only way to get more gain from a VHF or UHF antenna is to buy a beam antenna, and if you do, get one with as high of gain as possible.
For 800 MHz, get a catalog from L-Comm, they have antennas for the 800 MHz band with up to 11 DBI gain for under $60.00 and they work great, are compact and tough as nails. They have quite a big choice of antennas also. WWW.L-Com.com The antenna I mentioned is a Log Periodic yagi, perfect for pointing at your city or county emergency services building antenna
L-Com has a lot of equipment for the 800 MHz range on up, very good catalog with decent prices for quality equipment. The Tram antenna will not work at all in the 800 MHz range, you need to get an antenna for that range.

You do realize that these are all transmit and receive antennas that you have talked about, if you plan on never transmitting, For receive only, get the catalog or go on line to Universal Radio and buy the Comet D-130NJ antenna @ about $112.00. It has the "N" mount for the coax which is the best mount for the 800 MHz and under frequencies (much better than the UHF connectors. It is a very wide band discone and will receive everything that your scanner or radio will receive. They are tough antennas that will hold up a very long time, and if need be, you can transmit on it, but it's made for receive. You still want to use the LMR-400 coax. It's available from www.DXENGINEERING.com Other coax will lose well over twice as much signal between the antenna and your radio, it's a must have for the most signal to your radio.
Get their catalog, they sell the coax in different lengths, some with the ends already on the cable. You would have to buy the end that fits your radio and cut off the one N fitting and put the end that fits your radio on the cable. If you have never put ends on coax, find a Ham radio operator to help you, it will go far easier. Or, you can buy the cable without ends and put them on yourself, but I'd get the length of coax you need with the N connectors, that way, the one connector will already be on. The N connectors are waterproof, the UHF are not, but still buy the special tape for sealing coax connections and seal the fitting at the antenna. If water gets in the coax, it will ruin it. The tape is about $6.00 and worth it.
Don't forget to ground the coax or else remove the coax from the radio when not in use or when there is a thunder storm and put the end of the coax outside where it's dry if you choose not to use a lightning protector. They also get the static electricity off the coax that you get from wind blowing over the antenna. The voltage just from the wind can be dangerous. DX Engineering sells the Dimond lightning arrestors, hook it up to an 8 foot ground rod, pounded all the way into the ground right outside of your house and connect the grounding rod to the protector with #6 copper wire, you should get the one with "N" connectors and you'll need 2 more "N" connectors to hook it up to the coax. It would really be best to have someone who knows radio very well to help you install the antenna. DX Eng. also sells aluminum poles at very good prices if you need a pole for the antenna, but it sounds like you may already have one. If so, move it as close to where the radio will be inside the house for the shortest run of coax. This will all cost some money, but it's a one time deal and worth spending the money for your safety and best performance of your antenna. Most people do it the cheapest way. If you do, you may be OK, but just a close by lightning strike can blow up your radio, start a fire or hurt or kill anyone near the radio, a direct hit will do all of the damage mentioned and maybe more. This is nothing to take lightly, though most do. You will almost never find an Amateur radio operator who will not take these steps and more, they know the facts and a scanner radio will act just like a Ham radio to a lightning strike or static electricity.

73's John