berkinet

Yes. Put very simply, no antenna has any gain as they are passive devices, they simply radiate. True gain requires amplification. What is called gain in an antenna is really apparent gain. That is, the the strength of the received signal, either at or from the remote radio is compared to the signal received using an hypothetical lossless antenna that radiates or receives signals equal from all directions - above, below and from the sides. If an antenna's design favors signals transmitted or received from some particular direction, or directions, then at the same time it is reducing the signal transmitted or received from some other direction. The result of changing the radiation/reception pattern results in signals from/to some direction(s) being stronger than from others. Thus the apparent gain. Your doughnut radiation pattern favors signals from/to the sides and reduces signals sent/received vertical. It is a little bit like adding a lens to a lamp. A bare bulb (theoretically) radiates light in all directions. But, by placing a reflector behind the bulb and a lens in from of the bulb to direct the light, you will have much more brightness in the direction the lens faces, and much less light behind the reflector. But, the actual light output from the bulb remains unchanged. In fact, Yagi design directional antennas use elements with those exact names: directors and reflectors.

And, that is true. However, the issue I was raising was, is a flattened radiation pattern really the best choice for your application. If you are in hilly our mountainous terrain (you are in Nevada, right) then a flattened pattern may not be the best choice. However, in the end, the small differences in radiation would probably make no discernible difference. That is why I'd go with the lowest cost solution - for this application. Now, if you were a delivery driver in Kansas, maybe a hi-gain antenna would make a real difference.

BTW, I honestly don't understand why you just don't go with a simple 1/4 wave NMO mount antenna. They are dirt cheap, and easily replaced. A fiberglass antenna, no matter how rugged, will shatter if it hits a low hanging branch, overhead rocks, or even the ground (for flipper). A simple metal 1/4 wave will just bend over and can be straightened out in seconds (or replaced with a spare).

You have mentioned the suitability of an antenna for repeaters and simplex as though the two things are inherently different. Well, to some (very tiny) extent they are, in that with a repeater your transmit and receive frequencies are 5mHz apart, so there is a small degree to which an antenna might be tuned differently depending on whether the main use was simplex (tuned right on frequency) or duplex (somewhere between the Tx and Rx). But, that is really pretty insignificant. On the other hand, an antenna's radiation pattern can make a difference depending on the physical relationship between two stations talking simplex, or a station talking to a repeater. But, since many repeaters are actually located pretty close to the ground, like on roof tops, and two stations on a jeep trail could be several hundred vertical feet apart, you can't really say any particular "gain" pattern is better for one or another. However, as others have noted, a simple 1/4 wave may well be the best compromise, especially in a situation where both stations are in motion.

I don’t really have any comments if the questions you have posed. However, I would suggest you might get more responses by starting your own topic for this discussion.

Did you read the product description on Ebay?

I have no doubt the radio will meet your needs. ICOM builds a solid product. I suspect you could do a little better on price if you looked at other similar quality radios, like: Motorola, Vertex Standard (now Motorola) and Kenwood. But, it is new and you know the radio. So, as long as you can program it, or get it programmed, I don't see any issues. However, the radio, while Part-90 certified, is not Part-95 certified. So, if you care about things like that, well this won't meet your needs. On the other hand... Well, that's up to you

Now that Hans has shown you where the resistor is, I can tell you it’s usually best to just snip one side and then bend the resistor up rather than getting a soldering iron in there. The front panel programming is for making changes like frequency or PL on the fly, it doesn’t really replace software programming for setting up a radio in the first place.

Fixed. Thanks for noticing that.

Well, I can't say I agree on your first point (see below), but, I do agree whole-heartedly with your conclusion. Agreed. In open space, VHF will travel further, have lower path loss and better building penetration than UHF (See this paper for more information). On the other hand, UHF may actually work better inside a building because of signal splatter and reflection.

For a little more information on ground planes take a look at this page from stackexchange. Note in particular the first answer.

Heaven, and the powers of the universe, tend to help those who help themselves. This is a corollary to "google is your friend." With a few keystrokes I found https://www.dxing.com/radterms.htm and https://en.wikipedia.org/wiki/CQ_(call) Note CQ is not generally used on GMRS. Though, there is no legal reason you couldn't use it, other than most people listening would think you were daft.

Yes, any or all of the above. Each channel can be any combination of frequency (GMRS channel), name, bandwidth, power, and tone/code. You could even have the same frequency, bandwidth, power, and tone/code in two different channels with two different names, though that would make little sense. You could also program all 128 channels to the exact same settings (I.e., make the radio idiot proof). The only limit is the max number of 128 channels.

The KG-805G does not presently have the ability to do Talk-Around. The best you can do is to create two separate channels. Eg. ch 1, GMRS 22 Repeat (+5mHz) ch 2. GMRS 22 Simplex I have already suggested to the vendor (BuyTwoWayRadios) that they add Talk-Around as an option for the programmable function keys. They liked the idea and said they'd look into adding it in some future update, though I wouldn't hold my breath.

Yes.

The objects you n note may affect your overall transmission, but are fairly faraway and unlikely to impact SWR. As for the ground plane... The keyword here is plane, as in geometry, a flat surface. Your radials are creating the effect of a ground plane without actually creating the full plane. More radials would make the ground plane a but more effective, as would a solid metal disc. But, the difference would be negligible. However, keep in mind what I and others have noted above: 1.5:1 is quite good. You could spend a lot of time, and money getting it better and probably see no effective difference. Given the kinds of questions you are asking, I would suggest taking a look for some ham radio license study guides on antennas. You don't need to go the full route for a ham license (though that wouldn't be a bad idea). Just look for some basic on antennas

Regardless of which portable you end up selecting, it will work much better in your car with an external antenna. Just for starters, the antenna will be located higher and free of the metal cage of the car body. Also, if your portable's antenna is a stubby or rubber duckie variety, a 1/4 wave will significantly put perform it.

You are already in pretty good shape. Dropping below 1.5, even to 1.0 won't make a substantial increase in performance. It's not nearly as noticeable as, say, going from 2.0 down to 1.5. But, if you want to try for some small improvements... In general, I don't think you can have too much ground plane. (And I am sure someone here will correct me if that is wrong.) So, I'd extend the ground radials as much as possible and see if that makes any difference. Also, you don't mention it... but, are there any other vertical metal poles or other antennas anywhere close by? Other objects might affect your transmission and SWR.

I have no specific information on the radio you noted, and I am not very knowledgable on Kenwood products. So, consider my two comments as very generic... If you have, or think you might someday have, an interest in ham radio, you might want to look for a radio that covers both the (US) ham band (420-450 mHz) and GMRS band. Other than that, the radio you noted supports trunking. Since trunking is not used on GMRS, you might possibly find a non-trunking radio at a lower cost.

Yes, absolutely.

Are you suggesting a 20 pin connector? Or, do you really mean creating your own parallel interface? If you mean the latter, well I would be fairly sure that what you suggest cannot be done easily. On the other hand, if you just want connectors on the radio and control head, that should be pretty simple. I'd use two short ribbon cables at the body and head. One end connected to the respective unit, and the other terminated in a standard 20-pin female ribbon connector. Then just make a ribbon cable of the length you want and terminate it with a 20-pin male connector at each end. http://www.pacificcable.com/photos/IDE20.jpghttp://www.pacificcable.com/photos/IDH20.jpg

Hmmm... if the photo below (from radioaficion.com) is accurate, the control head is connected to the body with a 20 conductor ribbon cable. And, the part of the body that mates with the control head seems to have some sort of a bulkhead. You might just be in luck. Of course, there might be all kinds of RF issues if you lengthen the ribbon cable. But still... http://radioaficion.com/cms/wp-content/uploads/2018/10/AT-D578UV_teardown-3.jpg

Well, depending on how daring and capable with tools you are, you might want to just open the radio up and see what exactly connects the front section to the rest of the radio. It could be just a simple ribbon cable, or it could be a myriad of wires. If it is a ribbon cable or similar you might be in luck. Of course, you would still have to rig up some cover for the back part of the radio and something to cover the back of the face plate portion. if you do open the radio, please post pictures of the inside. Good luck.

You might want to Google for: ​"review" anytone AT-578UV and look on the forums at QRZ.com. There doesn't appear to be any major issues with the radio, but several little things.