Lscott

Are you sure the replacement antenna is really 4 db? A 1/4 wave on the 33cm band is around 3 inches, more or less, for a portable radio. If it’s really a gain type antenna is would have to be noticeably longer.

I would be VERY careful mounting a tall antenna on an aluminum roof top. Torque from highway speeds hittong the antenna on tree limbs etc. can damage the roof. Even people with a steel roof had sheet metal damage at times. The sheet metal used on many vehicles now days is rather thin. You should consider using some extra bracing under the area where the antenna mount is installed. A few antennas have an optional spring at the base that does a good job of saving your roof top in case of an accidental contact between the antenna and the obstruction. The major advantage to the “ghost” antenna is the very low profile. You can almost forget it’s there as far as pulling in to a garage, parking deck, drive throughs etc. However they are not the best antenna for long range communications. If you have just a few feet of extra coax I would just neatly coil it up and stuff it out of the way. A lot of extra coax you might want to consider cutting it shorter and installing a new connector on the end. Most mounts use RG58 coax which is rather lossy at UHF frequencies.

I don’t believe using a radio in SFR mode requires all radios to be from the same manufacturer. They simply would be required to adhere to the tier 1 and 2 DMR standard. Only the single radio functioning in the SFR mode would be communing with normal DMR radios. With the current rules a conventional analog in-band repeater requires two distinct frequencies, one in the 462.xxx range and the other in the 467.xxx range. So you have two frequencies used to support only one voice channel. Using a SFR one could operate two repeaters, one on a 462.xxx frequency and the other on a 467.xxx frequency. You now have doubled the number of repeaters without consuming additional spectrum. On simplex a number of radios can use what is referred to a Dual Slot Direct Mode. Apparently there are radios that will sync to each other using only one time slot without the requirements of a repeater to supply the time slot sync. What this does allows two such radios to use a single simplex frequency using just one of the two time slots. Another two radios on the same frequency could use the other time slot thus doubling the number of effective voice channels, again without consuming addition spectrum. https://blog.retevis.com/index.php/whats-dual-capacity-direct-mode-dcdm/ https://www.kenwood.com/usa/com/lmr/tk-d240v_d340u/

What would intrigues me about DMR are some of the radios that will function in SFR, single frequency repeater, mode. Of course you have to find one that works. Anyway the attraction is no requirement for using any kind of "cavity" filters which would be necessary on a more traditional in-band system. This means almost anybody could setup a repeater with far less technical expertise required and cost for a decent set of BPBR filters. So until the FCC changes the rules we won't have DMR on GMRS. I do expect that to happen sooner or later, likely much later.

The radio is D-Star, not NXDN. It's also a tri-band with two RX sections. https://www.kenwood.com/usa/com/support/pdf/TH-D74A.pdf The problem with digital radios in general, at least the hand held ones, is they support typically just one digital mode. So if you have an interest in several digital voice modes you're stuck having to carry around several radios, one specific for each mode.

Just a data point here speaking about some Ham HT's. My TH-D74A does multi mode RX from HF up. The scan speed on it is around 20+ channels per second, I've timed it. Its the fastest scanning radio I got. Of course it's not cheap either. About VFO's, yeah I rarely use one. Just about any frequency I'm interested in is programed in one of the memories.

I had a Ham buddy at work that picked up a few of those ultra cheap BF-888S 16 channel UHF "only" radios. Well it he found a code plug hack that would let it work on VHF too. To test it he did a test TX on a Ham 2M frequency in our south building while I monitored it in the north building. Yes it did work. But, this was the big one, I tuned to the third harmonic of the 2M frequency, which put it in the Ham 70cm band. I picked up the signal loud and clear! Needless to say I told him NEVER try to use the radio like that again. The crap coming out of that radio was a interference disaster. But what the heck, it was a cheap "multi-band" radio where you could talk on several bands all at the same time. A real bargain if you get what I mean.

Sounds like you're very well prepared! I think a number of first responders learned from the great north east black out and made better plans. What gets me are the some what frequent posts where a new GMRS user gets a radio for "emergencies" and seems to have no plans beyond that. No idea about how to keep the radios running when the batteries die. Not to mention things like heat, water and food if its really bad. Where I'm at the most likely case is a power outage. For that I have several solar panels, charger controllers and a collection of various sized LiFePO4 battery packs. Some of the radios will operate directly off of a 12VDC supply, others can use a 12VDC power adapter to recharge them. The nominal voltage for a 4S LiFePO4 battery pack is around 13.3 to 13.4 volts over most of the discharge cycle. When the pack is nearly dead the voltage is still up around 12.8 volts. The commercial HT radios I have need to use a charge cradle with a wall wart AC to DC adapter. I modified one charge cradle to add a pigtail with Anderson Power Poles, to interface with the battery packs, since it only needed somewhere between 12 to 15 volts max to work. So when the power fails I can keep the cell phone charged up, radios running and a few lights on using some low voltage LED light strips. I have a gas fireplace I can use for heat and stove for cooking so that shouldn't be a problem. I keep almost nothing in the fridge so I don't worry about that.

When we had the huge north east power black out years ago many people didn't. And those that did had no idea where to go or how far to drive to find gas. I knew of just one service station that had gas, and power for the pumps, and it was reserved for emergency first responders only. Even some of the cops I monitored on the radio where telling their dispatchers they had to walk to their current location, the patrol cars ran out of gas.

I would be rather suspicious of a perfect SWR reading of 1.0:1 across the band. That's something I would expect from a high quality UHF dummy load, and even most of those are not perfect either. I recommend you try another SWR meter. One thing people forget is test equipment will "LIE" to you, and very convincingly too at times! I have to deal with this from time to time since my position working in engineering R and D I have to provide support for our service group. It never ceases to amaze me when a service tech accepts what his test gears says, even when it makes no sense. I have the following in my sig file for my company email. “There are lies, damn lies, and then there is what you see on your scope’s screen.”

This is spec’ed for the Ham Bands only. https://mfjenterprises.com/products/bd-35 For wide band use you will likely be stuck using a mono-band amplifier. Some cheap ones are found here. https://baofengtech.com/product-category/amplifier/ You can use a couple of VHF/UHF diplexers, one on the inputs and one on the outputs, to build effectively a dual band amplifier. https://mfjenterprises.com/products/mfj-916b If you’re worried about drawing too much current from an accessory plug just turn the HT’s power output down to limit the amplifier’s output power and thus the current draw. Oh, the amplifiers are not “linear” since most Ham communications on VHF and UHF along with GMRS/FRS uses FM modulation so the amplifiers are designed for “class - C” operation, which is nothing close to linear. This is done to get higher efficiency. https://www.electronics-tutorials.ws/amplifier/amplifier-classes.html

Thanks for the detailed write up! I’ll have to go over it in more detail later. Out of all the CCR’s you tested which seems to be the best?

I may have mixed up the two . My idea concering the MXTA26 is it might be more sensitive to mounting location compared to other antennas. I noticed this when doing some testing on a Comet CA-2x4SR antenna, also a 5/8 wave gain antenna. The SWR varied depending on the type of mount and how the ground plane was laid out. I tried a couple of magnet mounts on my Jeep along with one home made mount using ground radials bent down at a 45 degree angle on a metal stand in the house. The last one seemed to work the best. In my case I also used the RigExpert analyzer, mine is the AA-1000 model, so I'm familiar with what they can do. https://cometantenna.com/wp-content/uploads/2013/09/CA-2x4SR.pdf

No problem. I've had dead links before where the cut and paste from the browser's address bar didn't copy the full link. I just wanted to be sure.

If you mean by "bubble pack radio" the ones you see at the department store I would say no. The FCC changed the rules back a few years so combo GMRS and FRS radios are no longer legally sold, and a few I think did include repeater access. What you will find are likely FRS only radios which by law can't have repeater functions. I think your best bet is researching online specifically for GMRS radios, then look carefully at the spec's or get a copy of the operator's manual. Check to see if repeater setup or functionality is specifically mentioned and how it works. As you discovered some don't. One more thing if you want repeater access have you checked to see if there are any repeaters, and are operational, within a few miles of where you plan to operate? If not then repeater functions on the radio won't help you much. Any handheld radio you do get I would recommend it should have a removable antenna. This way you can use it while mobile with a simple 1/4 wave magnet mount on the roof, or switch to a better on-radio antenna. The range is severely reduced using the on-radio antenna while inside of a vehicle. Some people use a magnet mount on a cookie sheet for a ground plane to use inside the house for limited range, usually better than the on-radio antenna.

I just tried all three links just now and they all work. Perhaps you need to try again or another browser.

This is a link for a commercial RF sampler, "ISO-Tee", connector. https://www.rfparts.com/rfa4059a.html

Just for my info can you provide some details on how you performed the tests? For a home made iso-tee connector they have to be calibrated, from some sources I've read, before each use. I found a nice write up on how one guy did his testing along with photos for those who might like to know how its done. Also how somebody made their own iso-tee connector. I'll admit it's done with a crappy "UHF" type connector but it's just the general idea. http://www.repeater-builder.com/antenna/desense-testing/desense-testing.html https://urgentcomm.com/2007/09/01/every-toolbox-needs-one-of-these/

The point about over paying for commercial quality Part 90/95 radios, yes some do in fact have both FCC certifications, should not be poo-pooed, especially on places like eBay. Personally I've purchased somewhere around a dozen such radios, hand held models - all Kenwood, to add to my collection. I've seen the exact same models selling for a good price to nearly 4 times more in the same condition. Some are listed as non functional or damaged but the seller still wants way more that other sellers that will guarantee their radio will work or you can send it back for a refund. Go figure. I see overpriced radios, functional or not, being relisted on eBay over and over again. Just for fun I keep them on my watch list to see how long they last before the seller gives up or gets reasonable with the price. Some of them have been relisting for almost a year at the same over priced point! A few times I've sent the seller a private message through eBay offering what I think is a good price. I've gotten some very good deals this way. I try this even if the seller doesn't have the radio listed for bids or best offers, just a fixed price. A few took my offer since they just wanted to get rid of the radio and not looking to make huge profits off the sale. Most just say no or ignore you. Then you wait to see how long it takes for reality to set in and they drop the price on their own. 8-)

I couldn’t agree more.

If you don't have (1) the right equipment and test jigs to make accurate measurements and (2) the experience/expertise to do this then I recommend you don't try it. Your typical HT antenna is a 1/4 wave long without internal loading coils. For GMRS frequencies the antenna should be somewhere around 6 inches long without any loading coils. So if somebody cut one down to 1 or 2 inches they very likely screwed up the measurement and or the test jig was very seriously miss designed. I have seen "special" 1 or 2 inch long UHF antennas. They have a construction where they have a build in loading coil to provide the inductance lost due to the antenna being shorten. These antennas are VERY lossy and are likely not much better than a dummy load screwed on to the radio.

I looked at a photo of the antenna base. Given it's a gain antenna I'll guess the first section is maybe a 5/8 wave. A 5/8 wave antenna needs a very good ground plane right at the base of the antenna. Using the mount you have, while it is "electrically" grounded through the set screws may not be sufficiently close to the antenna base, where the matching section is located, to function as a good ground plane. You can check that by using an NMO magnet mount type base located in the same position where the current one is located.

I went and downloaded the brochure for the EVX-531. It looks like a dead ringer for the Kenwood I have coming, about the same feature set but with a bit more output power, 5 watts verses 4 watts, which likely isn't that noticeable in real use. For anybody that is interested the brochures are located here. Both seem like nice radios. EVX-531: https://www.buytwowayradios.com/downloads/dl/file/id/747/product/3688/vertex_evx_530_series_product_sheet.pdf TK-D340U: http://comms.kenwood.com/common/pdf/download/DMR_TK-D240V_D340U_K_letter_1124.pdf

The Kenwood is only costing me $46 including shipping. I located the programing software on line as a free download with the SN required for installation. I’m not against Motorola gear, but I have a collection of Kenwood accessories that works with all the various models, except for the TK-2140/3140’s that need the “Motorola” multi spring pin type connection. The same accessories, including the programming cable, also work for the few CCR’s in the collection. Having to deal with 5 to 6 or more battery pack types and charges the various radios use is a pain already. I have a pile of used battery packs that I don’t have a good measurement of the remaking usable capacity. I’m looking at buying a good new programmable electronic load with a battery capacity test mode. Also can use it for running tests on solar panels. The typical end of life, EOF, for a battery is when the pack reaches 80 percent of the as new rated capacity under standard discharge conditions for the battery chemistry. Any at the point or less I’ll have to decide if it’s worth keeping for short term operation and testing or goes in the trash bin.

I'm picking up a used Kenwood TK-D340U Type-1 analog/DMR radio on ebay for a good price and I'm looking for a PDF of a good programming guide specifically for this radio. I have plenty of general DMR guides already. I also have the software too, but could use a more detailed guide on the feature set this radio has. The included help file is very brief and light on details. I have programmed a D878UV so a number of the DMR features I do have an idea what they are but Kenwood likes to relabel them using different terminology it seems. I want to make sure I know what the settings do before trying to put the radio on the air using a "from scratch built" code plug. The radio is interesting since it does both analog and DMR, 32 channels total in two zones of 16 each, and wide or narrow band analog. Each memory can can be programmed as a mix mode, DMR in and analog out, analog in and DMR out, or strictly analog or DMR. It also supports the Dual Slot Direct Mode as well. Another point of interest. I can enter out of band frequencies, with a warning popup window, but seems to take the entry. I'll have to wait and see how far I can push the out of band operation limits. I have read with many Kenwood radios it's around 5 percent so that would cover the upper end of the Ham 70cm band, which is all I'm interested in. https://comms.kenwood.com/common/pdf/download/DMR_TK-D240V_D340U_K_letter_1124.pdf