GMRS Yagi 7 element beam

[Guest By WRYF379]

By no means am I an expert but I have had some years of amature like radio and antenna experience.  Most of it 11 meter and antennas including a 6 element Quad beam.  The rest on State Government radio use mostly in the deep canyons of Central Idaho on the Little Salmon, main Salmon, South Fork of the Clearwater , Clearwater and Locksaw Rivers.  After the FCC required the State to tighten up it's Band Width, it made it much more difficult for us to hit our repeaters on HT's (hand held) and the more powerful mobiles also had more difficulty.  Having delt with this change, it became an educational experience and was frustrating when dealing with emergency and normal Comm's where you used to get out but no longer could.  State Comm as very supportive of us as you could ever wish for also faced the same frustrations trying so hard to pull us out.  The HT's and Mobiles and I forgot our Base units as you would expect were all  omni directional antennas.  I did get to visit one of our repeater towers on a mountain top and they were all omni directional as well. 

Where I'm going with this though is folks out there doing strictly GMRS may want to consider the advantages of Yagi or AKA, Beam antenna.  As best as I can determine in the Rules, GMRS radios are allowed to detach and use another type of antenna. The more elements in a Beam the more directional they become and the more elements they sort of speak in theory, naturally amplify transmit and recieve more than a omni dirrectional.  My GMRS Beam is a 7 element and has a perfect SWR match, 1.01:1, did not even have to adjust it, and I mounted it to a camera tri-pod for stability, don't have to hold it.  I was on a hill along the Highway near Butte City Idaho.  Knowing the dirrection of the Taylor repeater over near Blackfoot Idaho, I pointed it that way with the elements in the vertical position.  Now you read and hear all this stuff about how the GMRS frequincies are only line of sight but I had no line of sight due to earth horizon line of sight, some sources indicate it at just a little past 3 miles standing I think it was 5 foot 7 inches above ground combined with the terrain of the Snake River Plains between the two points though my elevation was 5439 feet and Taylor 545 feet higher at I believe was 68.8 miles away as the crow flies.  Higher terrain in between than what I had I'm sure would have had a much lesser outcome, is the nature of the beast but not so completely.  I listend to the use of this repeater that far away and heard both sides of the conversation two people were having.  I did not try using this repeater because I have not asked permision to use it but I was certainly impressed with my tiny Boefeng UV-5R GMRS only, is not HAM, and the GMRS 7 element beam.  Getting it pointed to the best signal, I saw out of 4 bars,  2-4 bars but mostly 2-3 and the two repeater users were mostly clear though I think were possibly mobile. 

My interest mainly is Simplex contact in irregular terrain like here in Idaho because it challenges the operator and antenna, is not as easy as hitting Duplex repeaters and I can not afford a repeater. Like it is said, antennas are 90% of the radio.  One other consideration is the side and rear of the beam antenna are less responsiive but also depending on how close to you other Comm traffic is.  I live remote so I have no experience to share if this 7 element beam was in a FRS/GMRS radio traffic congested area.  It could however be of benefit to add to your GMRS gear for the outdoors explorer and may possibly help to some degree pin point someone in distress as it is more directional than your omni dirrectional.  It's also not so big it is a pain to deal with.  Is amazingly small throw it in the front or back seat with a camera tri-pod.  The only problem I had was radial #6 could not pass through the hole during assymbly due to a rivet end slightly blocking passage.  I simply took a small file to it with a few passes and in it went. 

Dont be afraid to learn about your antenna options out there for GMRS and have a blast doing the FRS/GMRS thing out there.  WRYF379 out of service.   

[WRWE456]

Yup, I use one as my main base antenna. Also have a copper tube j-pole on top of the same mast. I have not noticed much reduction in reception in the null directions and to the rear as compared to the omni j-pole. Mine is the Arrow Antenna 7 element. Very nicely built. I'm on top of a 500 foot hill and most of the traffic I want to hear is within about a 30 degree arc so the Yagi is well suited for my application. I have tried rotating it but seems to make little difference. I pick stuff from all over the Puget Sound. I live in the San Juan Islands WA. I was listening to some mountain climbers this morning up on Mt Baker. They were on channel 7 simplex. That is about 60 miles from me and the Yagi is not even pointed in that direction. Seattle area repeaters come in loud and clear.

[Guest By WRYF379]

On 8/12/2023 at 5:39 PM, WRWE456 said:

Yup, I use one as my main base antenna. Also have a copper tube j-pole on top of the same mast. I have not noticed much reduction in reception in the null directions and to the rear as compared to the omni j-pole. Mine is the Arrow Antenna 7 element. Very nicely built. I'm on top of a 500 foot hill and most of the traffic I want to hear is within about a 30 degree arc so the Yagi is well suited for my application. I have tried rotating it but seems to make little difference. I pick stuff from all over the Puget Sound. I live in the San Juan Islands WA. I was listening to some mountain climbers this morning up on Mt Baker. They were on channel 7 simplex. That is about 60 miles from me and the Yagi is not even pointed in that direction. Seattle area repeaters come in loud and clear.

Have played around with this TC-YG07, could be a copy of the Arrow 7 element beam, seems to be well built,  more since my last Post and have found the closer to other GMRS comm, mainly local, one instance as far as about 23 miles so far is NOT so directional as we may want to expect with the much closer Comms.  Could be though a beam without any electronic amplifier, on it's own design amplifies incoming signals as well as out. What I have found though is it is directional on distant Comm, in my case one GMRS repeater at 68 and another at 97.31 miles away and neither are line of site and I can hear them clearly vertical element. Rotate the beam horizontal element and both repeaters fade out completely. Move the beam to one side or another in vertical element, never checked how many degrees, and the Comms fade out to nothing on the sides.  This is what I would expect with eperience using a 6 element quad 11 meter beam.   The rear however does recieve but I know how to close that up and may could help the local comm dirrection issue.  So far as it is, it is obvious to me the direction most receptive if distant by Sound and the Signal strength bars on radio.  I do NOT have access to either of these GMRS repeaters, have not requested permission from owners,  so have no idea yet if I can hit and open them with hand held 5 watt on the beam or the mobile 40 watt on a mobile dipole at such distances listed above.  

Of interest to me is I have found an unlisted GMRS repeater with my beam.  Using triagulation, both directions using terrain land marks on google map go to a location that I know has a repeater site that years ago belonged to a HAM operater.  Not only is it NOT line of sight from my place, I have a mountain between it and me and the site is 13.53 miles away as the crow flies.  In this case, the beam operated directional and only vertical polarity. I assume it is a very private repeater as it is seldom in use as well as not listed anywhere.  It's coverage though should be a great expanse over the Snake River plains of South East Idaho a 100+ miles give or take outer laying canyons and mountains in all directions.   

For me a beam is a must have antenna and is fun to see what GMRS comms you can find a direction for.  In my area, GMRS and FRS use is pretty slim most days but picks up during hunting seasons and farming.  Now and then truckers and other travelers 2 or more rigs seem to come through using them.  Here on dipole I'm sure is much more quiet than Sea-Tac.  

.  

 

[WRKC935]

So there are some issues using a beam specifically with simplex operations.  First issue is beamwidth of the antenna.  Think of an onmi-diredctional antenna as a bare light bulb, the light comes out in all directions pretty much equally.  Then we get into a short yagi of 3 or so elements.  That's like having a flashlight.  It's a directional beam of light that spreads out as the distance increases but is still very directional as compared to the bare light bulb.  Now we get into the longer boom yagi's.  And while 7 elements isn't really a big beam as opposed to some of the 30 element ones that ham's use for Satellite work, it's still significant forward gain.  That's gonna be like a cheap red laser that up close is just a dot, but at a distance, the dot might be a foot or two across.  You need to point that dot at the other person you are trying to communicate with and hold it on them throughout the communication as it progresses.  And the more elements, the smaller that 'dot' is that you need to hold on the other party.  Because once they are out of the dot, they are no longer able to communicate with you. 

 

Second issue is more of a regulation thing.  While the repeater channels are NOT ERP regulated and any sort of antenna system can be employed for these simplex channels, some of the simplex channels are indeed ERP regulated and the ERP is a calculation of antenna gain and input power to the antenna.  A 10 watt radio into a beam with 3dBi of gain is the same ERP as a 20 watt radio connected to an antenna with 0 dBi of gain (typically an omni-directional antenna).  If you get into 6 or 9 dBi of gain, your .5 watt radio is no 2 watts, or 4 watts, when you are regulated to .5 watts of ERP and FRS is always regulated on ALL channels hence the reason an FRS radio has an antenna that can't be removed and connected to a different antenna.

 

[Guest By WRYF379]

4 hours ago, WRKC935 said:

So there are some issues using a beam specifically with simplex operations.  First issue is beamwidth of the antenna.  Think of an onmi-diredctional antenna as a bare light bulb, the light comes out in all directions pretty much equally.  Then we get into a short yagi of 3 or so elements.  That's like having a flashlight.  It's a directional beam of light that spreads out as the distance increases but is still very directional as compared to the bare light bulb.  Now we get into the longer boom yagi's.  And while 7 elements isn't really a big beam as opposed to some of the 30 element ones that ham's use for Satellite work, it's still significant forward gain.  That's gonna be like a cheap red laser that up close is just a dot, but at a distance, the dot might be a foot or two across.  You need to point that dot at the other person you are trying to communicate with and hold it on them throughout the communication as it progresses.  And the more elements, the smaller that 'dot' is that you need to hold on the other party.  Because once they are out of the dot, they are no longer able to communicate with you. 

 

Second issue is more of a regulation thing.  While the repeater channels are NOT ERP regulated and any sort of antenna system can be employed for these simplex channels, some of the simplex channels are indeed ERP regulated and the ERP is a calculation of antenna gain and input power to the antenna.  A 10 watt radio into a beam with 3dBi of gain is the same ERP as a 20 watt radio connected to an antenna with 0 dBi of gain (typically an omni-directional antenna).  If you get into 6 or 9 dBi of gain, your .5 watt radio is no 2 watts, or 4 watts, when you are regulated to .5 watts of ERP and FRS is always regulated on ALL channels hence the reason an FRS radio has an antenna that can't be removed and connected to a different antenna.

 

You bring out a great point I honestly had not totally committed to GMRS memory. Got to always read the catch words. 

According to the Rules, CH1-CH7 on the Channel Chart limits FRS to 2 watts and GMRS to 5 watts "MAXIMUM PERMITTED POWER."  FRS are not allowed antenna changes so I would assume they meet the Rule requirement through engineering design and or a touch of de-tuning. As I believe you are pointing out, this MPP issue becomes a responsibility for any compliant factory GMRS transmitter and antenna combination user.  The Rule breakers will be Rule breakers but the unaware trying to be responsible operators I believe will give consideration to your point.  CH8-CH14 both FRS and GMRS are limited to 0.5 watts maximum permitted power.  In some cases, it is amazing what a 1/2 watt can do but is another subject. I would figure a compliant factory FRS would be a no ERP (Effective Radiated Power) issue in this channel range or one previous.  Factory built radios at least as I have read about are de-tuned a bit on power to avoid one of many FCC Rule violation fines.  Channels 15-22 are were I Simplex mainly off a 3 dB gain dipole and sometimes the 11 dBi gain Beam but do scan and listen to 1-22 either kind of antenna.  Using an on-line ERP calculator for my advertised 5 watt handheld in combo with the advertised 7 element beam specs, the ERP Watts are 38.38 based on dBi gain so I would assume I'm OK on CH15 thru 22 including 15-22 repeater as it limits GMRS to MPP of 50 watts.   Have not found though if MPP is calculated off dBi or dBd and seems there is considerable difference in figures once calculated.. To use this 7 element beam on my advertised 40 watt mobile on any GMRS channel would be a violation of the GMRS Rules.  The ERP calculator indicates it would produce 307.05 ERP Watts and also far exceeds it's design for up to 100 Watts.  I did not know just how much in theory numbers my beam would amplify TX power but I knew it would over a dipole and the more elements, the tighter the signal and naturally amplified, no added kicker.  It looks like the most you can go on a 5 watt is a 2.15 dBi gain dipole. For fun, it looks like a 0.5 watt radio on this 7 element beam would produce 3.83 ERP Watts so CH 8 thru CH14 would be off limits for that antenna use and a seller supplied little Rubber Duck would be perfect. 

Thanks so much for stirring the grey matter.  Putting some ERP calculation numbers to this realization of what GMRS channels allow for MAXIMUM PERMITTED POWER is eye opening once considering the antenna efficiency and radio power combo.  It's not all just the radio alone in GMRS. 

Merry Christmas and a Happy and better NEW YEAR!      

[WRWE456]

I only use the 5 watt minimum power setting on the KG-1000G. Have not needed more than that for my use, in fact the KG-935G+ works just as well on 5 watts. I don't use the .5 watt channels. The mobile rig will not tx on them anyway.

In my situation we are right next to Canada so can't work that direction anyway. The Yagi pointing South covers my local town and others all the way to Seattle.

[WRKC935]

21 hours ago, Guest By WRYF379 said:

You bring out a great point I honestly had not totally committed to GMRS memory. Got to always read the catch words. 

According to the Rules, CH1-CH7 on the Channel Chart limits FRS to 2 watts and GMRS to 5 watts "MAXIMUM PERMITTED POWER."  FRS are not allowed antenna changes so I would assume they meet the Rule requirement through engineering design and or a touch of de-tuning. As I believe you are pointing out, this MPP issue becomes a responsibility for any compliant factory GMRS transmitter and antenna combination user.  The Rule breakers will be Rule breakers but the unaware trying to be responsible operators I believe will give consideration to your point.  CH8-CH14 both FRS and GMRS are limited to 0.5 watts maximum permitted power.  In some cases, it is amazing what a 1/2 watt can do but is another subject. I would figure a compliant factory FRS would be a no ERP (Effective Radiated Power) issue in this channel range or one previous.  Factory built radios at least as I have read about are de-tuned a bit on power to avoid one of many FCC Rule violation fines.  Channels 15-22 are were I Simplex mainly off a 3 dB gain dipole and sometimes the 11 dBi gain Beam but do scan and listen to 1-22 either kind of antenna.  Using an on-line ERP calculator for my advertised 5 watt handheld in combo with the advertised 7 element beam specs, the ERP Watts are 38.38 based on dBi gain so I would assume I'm OK on CH15 thru 22 including 15-22 repeater as it limits GMRS to MPP of 50 watts.   Have not found though if MPP is calculated off dBi or dBd and seems there is considerable difference in figures once calculated.. To use this 7 element beam on my advertised 40 watt mobile on any GMRS channel would be a violation of the GMRS Rules.  The ERP calculator indicates it would produce 307.05 ERP Watts and also far exceeds it's design for up to 100 Watts.  I did not know just how much in theory numbers my beam would amplify TX power but I knew it would over a dipole and the more elements, the tighter the signal and naturally amplified, no added kicker.  It looks like the most you can go on a 5 watt is a 2.15 dBi gain dipole. For fun, it looks like a 0.5 watt radio on this 7 element beam would produce 3.83 ERP Watts so CH 8 thru CH14 would be off limits for that antenna use and a seller supplied little Rubber Duck would be perfect. 

Thanks so much for stirring the grey matter.  Putting some ERP calculation numbers to this realization of what GMRS channels allow for MAXIMUM PERMITTED POWER is eye opening once considering the antenna efficiency and radio power combo.  It's not all just the radio alone in GMRS. 

Merry Christmas and a Happy and better NEW YEAR!      

I mention the rules thing for one reason only.  If it's not brought to to the forefront in the initial discussion, then it will be discussed, debated, and pontificated by a number of folks that may or may NOT have a solid understanding of it and possibly convey partly or completely incorrect info that then needs corrected.  This always seems to turn into a thing, threads get hijacked, dead horses beaten.  It's just a thing that happens with online forums.  Nothing new or exciting, just a continuance of the norm.

Unless you are connecting your .5 watt radio to a 30dBi gain 20 foot dish and purposely creating interference for others I seriously doubt that the FCC is gonna come knocking. 

That being said.  You mentioned both dBi and dBd gain numbers.  Gonna give a quick explanation of each, because it's not common knowledge.

dBi is gain over an isotropic radiator.  This is the default 'paper' reference antenna that radiates RF in all directions at all angles equally.  It's basically a free space radiator that has a sphere of RF eminating from it.  I know that I used a lightbulb as an anology, and it's not quite correct since it can't radiate out the bottom of the lightbulb, but it's a good point of reference for most all other directions. 

dBd is gain over a dipole.  Dipole is simple, and does exhibit gain over an Isotropic radiator since it's pattern doesn't include significant radiation off the ends of the antenna.  That power has to go somewhere, so the increased radiation at certain angles give the antenna some amount of gain over the paper antenna in those directions. 

One of the other interesting things with antenna's an gain as opposed to amplifier gain which of course is an active component of the RF string is the amplifier is typically uni-directional with it's gain.  Take a typical amplifier with a 10dB gain design.  You put in 1 watt and 10 comes out.  This will make you be heard farther than before.  But it does nothing for your receive.  Now, gain in an antenna doesn't so much 'boost' the receive signal.  The signal is what ever it is at the antenna.  Once again, we bring in the light source.  The light isn't brighter for the directional antenna vs the onmi directional antenna.  It's the same level.  I am not going to bore you with math and what is referred to in the big antenna college text books as power density.  I am gonna go back to the simple light source.  So what a directional antenna does to increase your ability to 'hear' a signal is it darkens everything else out other than what it's pointed to.  Take a flashlight outside at noon, you can see it at 100 yards.  But you can't see a candle at the same distance.  There is too much other light source (noise) to see the candle.  But take the same candle out at midnight, and it can be clearly seen as a light source at the same distance.  The directional antenna does this by ignoring the light (signal) from every other direction and only looking at the candle.  A receive amplifier can't do that.  It's going to amplify the signal some, but it's going to amplify all the other signals that we don't want as well.

 

 

[WRPT980]

On 12/11/2023 at 10:17 AM, WRWE456 said:

I only use the 5 watt minimum power setting on the KG-1000G. Have not needed more than that for my use, in fact the KG-935G+ works just as well on 5 watts. I don't use the .5 watt channels. The mobile rig will not tx on them anyway.

In my situation we are right next to Canada so can't work that direction anyway. The Yagi pointing South covers my local town and others all the way to Seattle.

Wow! Thanks again. Great discussion your having.  The yagi I am putting on my house is a  5 element browning BR-6355 at 35 feet.  My 2nd mast I wish to put up on my shop  is 31 feet with a tree closely in the way of the direction I wish to aim before I get out. (past). So I am thinking of putting a 7 element yagi  there.  What thoughts would have on this.  And it is so hard for me to figure out which antenna.  I am looking for suggestions to check out. Again. flat between me an my target but lots of spotty woods and curvature of course. Hoping to reach 15 miles. I will wait until I test the house set up before I spend more $ on the shop . Both masts will have a Tram 1486 which  I tuned per instructions. I had it on house NOT tuned and now it works better

I gotta try at least and go from there.

THANKS EVERYONE.  Great place to learn.

 

 

[SvenMarbles]

It's what I do. 10 watts and 9db gain. for UHF it's all you need to be loud.

[WRXP381]

4 hours ago, WRPT980 said:

Wow! Thanks again. Great discussion your having.  The yagi I am putting on my house is a  5 element browning BR-6355 at 35 feet.  My 2nd mast I wish to put up on my shop  is 31 feet with a tree closely in the way of the direction I wish to aim before I get out. (past). So I am thinking of putting a 7 element yagi  there.  What thoughts would have on this.  And it is so hard for me to figure out which antenna.  I am looking for suggestions to check out. Again. flat between me an my target but lots of spotty woods and curvature of course. Hoping to reach 15 miles. I will wait until I test the house set up before I spend more $ on the shop . Both masts will have a Tram 1486 which  I tuned per instructions. I had it on house NOT tuned and now it works better

I gotta try at least and go from there.

THANKS EVERYONE.  Great place to learn.

 

 

Just get a 712 comet it’s 9bd and will blast 200mile in 20watts. Why do all this junk to get 15miles.  A hand held 5 w will do 30miles line of site.  Yagi is not needed to do 15miles in any woods.  Just put a 10’ comet 712efc as high as you can 

[BoxCar]

The antenna is more important than the power output of a transmitter.

[WRXP381]

Just now, BoxCar said:

The antenna is more important than the power output of a transmitter.

That’s what I always say. 

[AdmiralCochrane]

Completely different frequencies and propagation effects, but GMRSers might be suprised to learn on HF (short wave) some hams get lucky and bounce signals all the way around the world with 10 to 20 watts.  Back to relevant bands and frequecies, you can communicate with the ISS with a regular 50 watt VHF or UHF transceiver.  Using a Baofeng HT I have listened in on hams using the ISS repeater to make contacts with other hams.  Knowing the antenna polarization and sweeping thru the frequencies made it better as did waiting for a high overhead pass. 

It is about the antenna and knowing what to do with it 

[WRPT980]

13 hours ago, WRXP381 said:

Just get a 712 comet it’s 9bd and will blast 200mile in 20watts. Why do all this junk to get 15miles.  A hand held 5 w will do 30miles line of site.  Yagi is not needed to do 15miles in any woods.  Just put a 10’ comet 712efc as high as you can 

That would be awsome. I will check it out!

Thanks very much!

[SvenMarbles]

13 hours ago, WRXP381 said:

Just get a 712 comet it’s 9bd and will blast 200mile in 20watts. Why do all this junk to get 15miles.  A hand held 5 w will do 30miles line of site.  Yagi is not needed to do 15miles in any woods.  Just put a 10’ comet 712efc as high as you can 

There are all varieties of use cases for antennas. Yes that Comet 712 is a prime antenna. It's also a massive beast! It's an 11 foot tall vertical. Some people might not be able, or want to have such a prominent antenna. There's also the matter of needing very robust mounting for it, wind load, etc..

A UHF yagi on the other hand, is a small and light thing that can squirt the RF just as far and as strong with equivalent decibels, just only in the desired direction at the time. And it's the size footprint as a shoe box. If you don't mind going and pointing it at the repeaters or direction of receiving party, I think it IS an option for some to consider, again, if they might not be able to mount up a big ole 11 foot tall monster antenna.

In my case, I've already got other antennas for other bands and I was able to side-mount this one onto an existing mast in a way that it can swivel. I just take the parallel run of PVC pictured and give it a twist.  It's super simple to construct something like this, I don't sweat a wind load on it, and it'll get into a repeater 30+ miles out as good if not better than a 712 if I've got it pointed at it. They're also excellent on the RX side of things.

[WRPT980]

On 4/6/2024 at 7:46 PM, WRXP381 said:

Just get a 712 comet it’s 9bd and will blast 200mile in 20watts. Why do all this junk to get 15miles.  A hand held 5 w will do 30miles line of site.  Yagi is not needed to do 15miles in any woods.  Just put a 10’ comet 712efc as high as you can 

That would be awsome. I will check it out!

Thanks very much!

[WRYZ926]

The Comet CA-712EFC is a great antenna. How far you can talk to others will depend on how high the antenna is, local terrain, vegetation/trees, structures, etc. Don't expect to get a 200 mile range unless you live in the wide open desert or along very large lake.

[WRWE456]

Just did a test today using my KG-935G Plus hooked to my Arrow Antennas Yagi through 50' LMR400. Again I'm on top of a 500' hill in the San Juan islands with line of sight to Seattle but for a few trees in my neighborhood. Got a good signal report from a guy through the Tiger Mountain repeater 91 miles away. Not bad for 5 watts. Height and line of sight did most of it. Yagi needed? Maybe not but sure works good. Its a nice compact antenna also.

[WRPT980]

2 minutes ago, WRWE456 said:

Just did a test today using my KG-935G Plus hooked to my Arrow Antennas Yagi through 50' LMR400. I'm on top of a 500' hill in the San Juan islands with line of sight to Seattle but for a few trees in my neighborhood. Got a good signal report from a guy through the Tiger Mountain repeater 91 miles away. Not bad for 5 watts. Height and line of sight did most of it. Yagi needed? Maybe not but sure works good. Its a nice compact antenna also.

I think I will buy my second yagi browning br-6355 5 element. I went out to the 15 mile point today and have a browning yagi on teloscopic mast off the back of my pickup for now, aimed back at my house Tram 1486.   I think I will get a second one for the house which will aim at each other. Wondering if I should get a 7 element yagi instead of a 5 or keep them the same.  I know the beam width will be smaller with the 7. But for 15 miles, lots of spotty woods maybe I will just buy another browning BR-6355. decision's , decision's. Any thoughts out there? 

Thanks in advance

[WRWE456]

This was the first time I tested the 935G with that repeater.

[WRYZ926]

The KG-935G is definitely a good radio with a good factory antenna. I live in mid Missouri with lots of rolling hills and valleys and plenty of trees. I can get into the local repeater at 21.5 miles away with the 935G while outside in my yard when conditions are good. Getting into the repeater is easy when running my base radios  on low power or even the 935G connected to my base antenna. I am using a Comet CA-712EFC that is 18 feet above the ground.