tweiss3

It could. If I remember correctly, if looking for vertical isolation, you will need at least 10' vertically to get 60db, and that is directly vertical, one over the other. If going horizontally, I think it was something like 50-60 feet apart to prevent damage at 45 watts, but there may still be interference when transmitting.

Wonderful chose, both for quality and for price. Having local support via dealer is a plus as well.

https://www.fcc.gov/wireless/bureau-divisions/mobility-division/amateur-radio-service/club-stations There are a pretty decent set of rules to get a club license, all intended to keep a person liable for any operation under that call. The operator using that call must have permission to do so, and either have their license, or be operating under another licensed ham operator (they have to be present to maintain control of the station).

@JB007Rules 1-5/8" is nice. Did you pay by the foot, or did you end up buying that whole spool? I'm glad you have a cool tower owner/crew. Is yours the 100W version? Set right at 50W, that thing could key up for days. @WROZ250 My comments were never about the FCC actually doing something, or showing up, but on conversations I just had about getting on commercial towers with multiple people. Like or not, getting tower space is more or less not up to the system RF engineer, but in fact up to corporate lawyers, many of which wouldn't be able to tell coaxial cable from power cable, but their job is C.Y.A. for the business. If I had the opportunity he did, and could get away with that equipment, yes I'd go for it. But since this is a public forum, since any goof can pull this up from google, it does need noted that technically, its not compliant. @gman1971 You are correct, modified anything means it no longer has it's certification. There are plenty of options that will do in-band and meet the spirit of the rules without hacking them up. My big point is, with the difficulty of obtaining sites, lets not do anything that would make it difficult for people in the future to obtain space. I'm currently helping a group look for space, I'm part of another group that is currently month to month (no phone calls returned to get a new contract) that needs some long overdue maintenance, but is too scared to perform and get booted completely, three others lost tower space in the last year with no negotiations, just come get your equipment, not even a discussion about rent/terms.

The FCC memo you are thinking of said something along those lines, just if they end up coming after you, they can use it to add another charge in an attempt to make things stick. Because the FCC won't go after you, doesn't mean your lease won't get you in trouble. I've talked to a few local tower owner/operators that manage the RF engineering, and due to the liability to the company, everything would have to be by the book, including but not limited to correctly type accepted equipment, structural analysis of the tower, having to provide a separate shack and access without accessing the secured area holding the company equipment and shutoffs accessible by the company. Should you violate a term of your lease (I sure hope he read it completely), you could end up blacklisted and cause issues for other GMRS or ham users wishing to put up equipment.

I'm glad you have your system up and running. Its wonderful you got a good site, and yes, there is a massive difference between using a duplexer or combiner and having separate TX & RX antennas. What Coax did you end up with, 1/2, 7/8, 1-1/4? Also, did the tower owner stick you with the bill for the structural analysis, or did he let you split that with other users? Around here, that's usually $3000+, and a big issue. I do want to point out a handful of things that I think are important to note: 1) The quantar is a wonderful quality repeater that can take abuse. It is however, according to every FCC ID I have checked for the UHF quantars, none are certified for GMRS (Part 95). If you were running it at your house or private site, and kept the power to 50W, not a single person would batt an eye. But, being at a commercial site, it may be a target when tracking down issues on adjacent systems and sites, and someone may say something. 2) The quantar does have a better receiver than the TKR-850, but the older TKR-820 is right on par with sensitivity when tuned up correctly, and can match the power of the 850 without problems. It of course, won't hit the 100W output of the quantar ever, but that's not a problem in most cases. 3) The difference between Moto and Kenwood repeaters is indistinguishable when you start tossing in cheaper options, like Bridgecom, Retevis, etc. Of course, some sites have these cheaper repeaters, and they work wonderfully, but there is also significant additional infrastructure backing it up, like full size 6 cavity bandpass+band reject duplexers, pre-amplifiers, filters, etc. I'm glad you had success, and yes, its much more than just buying $1k in equipment, and the overall maintenance, upkeep is continuous. I do suggest you check your tower lease, and make sure you aren't putting yourself in a tough spot with the FCC certification, but keep on trucking. Getting a site and following through is tough these days.

@kidphc Yea, looking at Little Tarheel II/Baby Tarheel again. It would be an option for hatch lip mount. @marcspaz Removing the scanner in position 2 is a non starter. That thing has gotten me out of so many headaches while traveling. Getting a screwdriver would add 6-80 instead of just 6. This is my wife's car, and the two antennas up there are nearly invisible, and I'm not really interested in swapping out radios, as she has the hang of this one, I don't need to muddy that water. The idea of the third hole was I would trust it with a whip while on the trip, but then pull the antenna and cap it, not worry about anyone seeing it to tamper with. With a screwdriver, I could pull the antenna for the week, and reinstall for the return trip, but the whole mount would come out after, I don't need anything visible where one could tamper or have reason to mess with her car. I never intended to play around on FT8 mobile or anything like that, but it would be nice to have a setup that could be used in the future for POTA. I think all this points me back to spending $600 on a screwdriver antenna. Height above roof line would be more desirable as well (XYL approal).

I have a few road trips this summer planned. We will be taking my wife's vehicle. Transit Connect. Currently there is the primary 2m & 70cm (50 watts) antenna in location 1, and the scanner antenna in location 2. Between the scanner antenna, the primary radio (50W dual band) and roof luggage carrier. I was tossing up the idea of temporarily adding 6m to the car for a few road trips via 705 or 817 (10W max). I've thought of getting a tri-band antenna for location 1, but I can't find one I like or would trust for the whole trip. The Diamond/Comet options look problematic. Based on my research, the Larsen NMO50 whip is only good for 6M, not good on 2M or 70CM, while the NMO140 is good on both 6M (accidentally) and 2M, but not 70cm. I can't loose 70cm, as we will be using that for general convoy communications in the mountains. My only real option is placing a third antenna (likely NMO50) 20-22 inches from the dual band radio antenna, on the passenger side. While I'm not necessarily worried about the 10W of 6m getting to the other radio (or affecting its ground plane), I am worried about the 50W radio blowing through the front end of the radio used on 6m, even if it isn't resonant on those frequencies. What are my options? Annoyingly enough, all the 6m bandpass filters I find are only good for 50-52MHz, where half the intended use is above 52MHz. Also, what is the usable bandwidth of the NMO50, I don't see anyone mentioning that in the specs, though the cut chart indicates it might be pretty narrow. Second, and less ideal option would be to mount a MFJ MFJ-1606T 6M whip on the hatch, attached at the lower part of the hatch, and supported near the top, of the coil, below the whip part. The scanner scanner antenna should be protected as it has an RF limiter, but I don't want to pop that limiter, I think it's rated for 10W max.

I use Comet in my vehicle, and 60dB is enough isolation with commercial UHF and Yaesu VHF. A quick search of Tessco brings up one item: EMR $560 https://www.tessco.com/product/vhf-uhf-crossband-coupler-535434 Listed as still only 60dB isolation.

GMRS? Only if they are a grandfathered license. Without any license, they are able to use FRS, which as you should know, overlaps on all 22 channels of GMRS.

Are they as convenient as they seem like they should be? Looks like a good way to save tons of space, be hidden most of the time, and operate nearly identical to the HT. Too bad they double the cost of the radio, or they would be a no brainer.

That weight and size difference doesn't seem too bad. Its more of a width increase than anything. Speaking of MOL, does anyone use the HHCH (PMLN7131) with their mobile?

Does anyone have a photo of the R7 next to the 7550? I'm interested in a size comparison. IMO, the 7550 is the perfect size, especially in my Motorola chest rig, any bigger and I'd have an antenna in my neck.

It's $4k for the Bridgecom, Sinclair makes a nice cavity 4 channel that would work in this situation AND in a GMRS + ham version for $6k. Cost isn't everything, but the insertion loss is better with Sinclair, isolation is better, power handling is better, and its much more simplified.

Based on the specs from bridgecom, its 4dB (60%).

Yes, LMR400 will drop your loss from 60%+ to less than 30%.

Those Siro antennas look decent. Do they make a phasing harness? Their instruction provide spacing for making an array, but the biggest issue with an array is the phasing harness.

RG8U is good only for extremely short runs (like a mobile mag mount) at UHF frequencies. You are seeing 8.6 dB loss per 100' of cable, or greater than 60% power loss in the cable. Not only does that mean at maximum you are only transmitting 18W, but it also means that received signals are weakened significantly as well.

The thread here sparked an internal debate in my head. 47 CFR 95.1767(a)(1) states "The transmitter output power of mobile, repeater and base stations must not exceed 50 Watts." In the other thread, that version of the Bridgecom hardware provides 4dB of insertion loss before you even connect the antenna feed line, loosing 60% of your power right off the bat. In otherwords, before you eve get to feed line loss if you have 50W out of the repeater, you are down to 19W. Again, this further points to the importance of proper feed line choice and a great antenna (why skimp if you are already dropping $4k+ on a combiner). Even with hardline, you could only see 6.8W/10.7W/12.7W to the antenna with 1/2"/7/8"/1.25" on a halfway decent tower site (300'). Potentially, a manufacturer could potentially provide a 8U complete box with a single coaxial connector that puts out exactly 50W at that connector, but has all the combiner, transmitter & receiver in the single box, and if that enclosure package was tested and achieved the part 97 certification, would be acceptable for use for GMRS. The obvious would be that the transmitter would output higher than 50W to overcome the losses internal to the box, but since its "one piece" could potentially pass the transmitter based on that. This is slightly different from most repeaters, since the duplexer may have a spot in the case, the jumpers are exterior, and the rating is for the raw transmitter output before the duplexer. Now I have my opinion/interpretation, but I'd like to hear from others. Where is that power limit taken from and why? This is not to say that anyone would know/notice/care if you ran an amplifier to make exactly 50W come out of the duplexer or combiner. Not saying you should, but its not impossible, not that there are part 95 certified amplifiers available that could handle the duty cycle needed.

It's on their website: https://www.bridgecomsystems.com/collections/uhf-duplexers/products/bridgecom-bcd-combiner-duplexer So it appears they used two duplexers then added in the wide notch "combiner" which would balance the system and maintain 50 ohms. Here is their diagram: This group of hardware will not work for a ham repeater + gmrs repeater. This way only worked because the two repeaters were close enough to each other the wide notch duplexer could pass two TX on one channel and two RX on the other.

Do you have a link to the video? Most transmit combiners are not much different from duplexer cans. I'm not 100% sure, but I would think that for a two repeater system, you would need a 4-channel https://www.sinctech.com/collections/cavity-combiner-1/products/combiner-4-ch-8-5-cavities-dual-stage-7-16-din-406-512-mhz.

Repeaters are opposite of general programming, the TX frequency of a radio is the RX frequency of the repeater, and the RX frequency of the radio is the TX frequency of the repeater, for GMRS that mean repeaters listen on 467, and transmit of 462. In other radio services, the TX could be above or below the RX frequency, but it's laid only one way in the GMRS regs.