OldRadioGuy

You could use some heavier, lower loss coax for the middle section of the run where flexibility is not an issue.
Keep the thinner more flexible coax for a few feet at the ends where you need it more flexible.
This will keep your overall loss lower without make it unwieldy.
I would try to limit coax loss to around 3db if you can.   Lower is of course better.
Vince

Seems like you could just use your 440 MHz / 70cm ham antenna with a coax switch.
I've tested several of my hamband UHF antennas on GMRS and all seem to match up well enough.
Vince

Seems like you could just use your 440 MHz / 70cm ham antenna with a coax switch.
I've tested several of my hamband UHF antennas on GMRS and all seem to match up well enough.
Vince

After thinking about it..... a better way to put it is that there is no point in treating very short lines as T-lines.  There is no benefit in treating it that way.  In PCB and chassis  design it's mainly the delay of the T-line that has any meaning
When you design on a PC board, even at 1GHz you measure the S-paramterters on the PCB or at the PCB interface.  So all the parasitics related to the packaging and PCB interface are absorbed into the S-Parameters.  Matching network components are generally treated as discrete impedances - and this is pretty accurate.  Everything is surface mount today and the traces are typically as short as the pads.  Once we got past the matching network we would try to keep our microstrip in the ballpark of 50 ohms but in many cases you are only going an inch or two.  So if your microstrip is off 15% it's probably still better than your matching network. 
Even at a GHz PC boards have become too small to economically use stubs and T-lines for on board for matching.  You can buy an 0402 1pf cap or 1nH inductor for next to nothing.  PC board space is too valuable for stubs or T-lines of meaningful length. 
The only way to really see this is to plot it out on a Smith chart.   When the rotation is so small it just doesn't do anything. 
Vince

As others have said, these cables are really easy to get at Office Depot or BestBuy.
If you are looking for something special like a right angle or shorty or whatever PCH cables is the mother load. They are also dirt cheap.
https://www.pchcables.com/
I used to go in the store and get BNC cables, USB, Power etc..  It's a handy place.
The quality seem OK on everything I've bought there.

Just remember that higher cable loss results in BETTER SWR.... (but not better radio performance).  I do not necessarily think this is what's going on in this particular situation though.... unless something is really wrong with the cable itself or a connector is defective. 
Minimum return loss is twice the cable loss.  So if your cable loss was 3dB your min return loss would be 6dB which means the worst SWR you could ever see is 3:1 even with no antenna at all.  (Of course, no mobile install would have such a high coax loss with only 20' of cable.)
You can see this if you just install a 3dB attenuator on the SWR meter with nothing at all attached after it.  
Ham guys are often puzzled when they upgrade (a 75' run or whatever) to low loss coax then end up with a worse SWR.  The antenna was always a poor match but it was masked by the lossy coax.  Of course their radio will actually radiate more power than before with the better coax even with the worse looking SWR.  More power reaches the antenna and therefore  more power is reflected back.... with the same antenna as before.
Length of coax does not affect SWR at all except for the difference in loss associated with it.  It can however affect forward radiated power if your radio output is not a true 50 ohms... and most are not.  They are designed to "work into 50 ohms."  This does not mean that they "look like 50 ohms"  when looking back into the output port.   There may be impedances other than 50 ohms which result in better (or worse) power output.  I've seen this on my KG805G with a ham radio 70cm antenna and a certain length of coax.  The radio will actually put out more than the typical 4-5W with some lengths of coax. 
Of course the "wrong" impedance can also cause instability or excess dissipation so you want to operate your radio into something reasonably close to 50 ohms.  Any SWR better than 3:1 should be safe though.  Many low power hand held or mobile radios would be "safe" into just about any impedance. 
Vince

Harbor Freight has several "Jump Starter" battery packs with built in chargers.  You can just leave it plugged in and charging.
I have one and it works great (I do not use it for radio stuff so much so you'll have to check the specs)
Mine was not very expensive but they do not make that model anymore.
You could also just get an AGM (sealed) 12V battery and keep it on a low amperage charger.
This assumes you don't talk continuously on the radio. 
You have to do the math and see how much battery and what amperage charger you need.
 
Vince

That is called “desense”. The radio that is transmitting, although transmitting on a different frequency, is actually desensitizing the receiving radio thus rendering it incapable of extracting the desired signal. It is the same effect you and your eyes suffer when you look in the direction of a bright light. Suddenly your eyes cannot make out the detail of the less bright items around you until the bright light is gone.

The better the receiver design is within the radio the less it is affected by this.

As Skyline said, put some space between the radios so the off-frequency transmitting radio is “less bright” to your receiving radio.


Michael
WRHS965
KE8PLM

Your own test seems to answer the question pretty well.
Trees don't absorb 450MHz that badly unless they are just loaded with snow or something.   Maybe not even then.
Terrain is the dominant factor and higher power will just extend the fringe a small amount.
 
Of course there are different factors in different situations - like cars or houses blocking your signal.  You could also have beneficial reflections of your signal that help you reach over the horizon.  In these cases the high power could make a bigger difference.  I suspect in the city the higher power may be a bigger factor.  But it's very tricky to put a number on. 
Vince

Try Ham Radio Outlet.  They have quite a few.
Vince

There are switching converters in just about everything electronic - especially anything with batteries.  So you are already operating your radios in the presence of switching converters.  Your vehicle probably has several switching converters in it already.    I would be more worried about radiated interference than conducted interference.  If you have issues consider locating the converter in an area that is shielded from the antenna.
Switching converters can be very clean but higher power converters will make more noise.  I would by a quality brand.  Cheaper brands are more likely to cheat.
Chances are you will be fine with it but there is some luck involved.  Most switching converter noise (especially broad band noise) tends to be well below 400Mhz.  So I would be optimistic.  It'll probably be just fine.
Vince

After thinking about it..... a better way to put it is that there is no point in treating very short lines as T-lines.  There is no benefit in treating it that way.  In PCB and chassis  design it's mainly the delay of the T-line that has any meaning
When you design on a PC board, even at 1GHz you measure the S-paramterters on the PCB or at the PCB interface.  So all the parasitics related to the packaging and PCB interface are absorbed into the S-Parameters.  Matching network components are generally treated as discrete impedances - and this is pretty accurate.  Everything is surface mount today and the traces are typically as short as the pads.  Once we got past the matching network we would try to keep our microstrip in the ballpark of 50 ohms but in many cases you are only going an inch or two.  So if your microstrip is off 15% it's probably still better than your matching network. 
Even at a GHz PC boards have become too small to economically use stubs and T-lines for on board for matching.  You can buy an 0402 1pf cap or 1nH inductor for next to nothing.  PC board space is too valuable for stubs or T-lines of meaningful length. 
The only way to really see this is to plot it out on a Smith chart.   When the rotation is so small it just doesn't do anything. 
Vince

After thinking about it..... a better way to put it is that there is no point in treating very short lines as T-lines.  There is no benefit in treating it that way.  In PCB and chassis  design it's mainly the delay of the T-line that has any meaning
When you design on a PC board, even at 1GHz you measure the S-paramterters on the PCB or at the PCB interface.  So all the parasitics related to the packaging and PCB interface are absorbed into the S-Parameters.  Matching network components are generally treated as discrete impedances - and this is pretty accurate.  Everything is surface mount today and the traces are typically as short as the pads.  Once we got past the matching network we would try to keep our microstrip in the ballpark of 50 ohms but in many cases you are only going an inch or two.  So if your microstrip is off 15% it's probably still better than your matching network. 
Even at a GHz PC boards have become too small to economically use stubs and T-lines for on board for matching.  You can buy an 0402 1pf cap or 1nH inductor for next to nothing.  PC board space is too valuable for stubs or T-lines of meaningful length. 
The only way to really see this is to plot it out on a Smith chart.   When the rotation is so small it just doesn't do anything. 
Vince

After thinking about it..... a better way to put it is that there is no point in treating very short lines as T-lines.  There is no benefit in treating it that way.  In PCB and chassis  design it's mainly the delay of the T-line that has any meaning
When you design on a PC board, even at 1GHz you measure the S-paramterters on the PCB or at the PCB interface.  So all the parasitics related to the packaging and PCB interface are absorbed into the S-Parameters.  Matching network components are generally treated as discrete impedances - and this is pretty accurate.  Everything is surface mount today and the traces are typically as short as the pads.  Once we got past the matching network we would try to keep our microstrip in the ballpark of 50 ohms but in many cases you are only going an inch or two.  So if your microstrip is off 15% it's probably still better than your matching network. 
Even at a GHz PC boards have become too small to economically use stubs and T-lines for on board for matching.  You can buy an 0402 1pf cap or 1nH inductor for next to nothing.  PC board space is too valuable for stubs or T-lines of meaningful length. 
The only way to really see this is to plot it out on a Smith chart.   When the rotation is so small it just doesn't do anything. 
Vince

Here's something to ponder.
If a 2:1 SWR antenna were connected directly to the radio with no coax at all there could be no standing wave.  Standing waves need transmission line in order to exist.  A mismatch is still a mismatch even without a transmission line to allow standing waves.
You will still have the same loss of radiated power due to the same mismatch.  The standing wave itself is only a symptom of the mismatch.  The coax is just the middle man. 
When you have a "matching box" at the radio end of the coax things get really complicated.  There is still a mismatch between the antenna and the coax but the mismatch at the match box makes a "reciprocal" reflection that cancels out most or all of the bad reflection at the antenna.  The length of the coax will affect the match in this case.  This is why is it best to have the matching unit right at the antenna.   The icom AH4 does this for the HF bands and works very well with terribly mismatched wire antennas.  You do not see these things on the VHF/UHF bands where antenna size is not much of a problem.  Better to just make the antenna the right length.
Just some
Vince

The reason antenna (and therefor radio outputs) were designed to be 50 ohms is largely the coax.
50 Ohm coax is practical to make in manageable diameters and will carry decent amounts of power.  They determined that 50 ohm coax for a given size could carry more power than other impedances.  It was deemed optimum by some military research study.  Also, with low voltage solid state radios it works out very well. 
Once you choose 50 ohm coax for your radio system it makes sense to have the radio and antenna made to match it.
 
Of course there is 300 and 400 ohm twin lead transmission line (ladder line) and some radios used to be designed for it.  It made far more sense in the tube days to design higher Z finals on radios.  But that's mostly history - at least for our portable 12v radios.  
Most radio outputs are predominantly resistive impedance with little reactance (inductance or capacitance). 
 
Vince
 

I got my extra class ham license in 1985 and live out here in Spokane.
I often monitor the ham repeater system here that covers essentially the whole eastern half of Washington state.
I also belong to the Spokane VHF Club.
 
I find that most of the hams are surprisingly receptive to GMRS and many (or most) of them have their GMRS license.
They talk about GMRS on the ham repeater now and then.
They also have discussed it on the VHF club net and at meetings.
 
The reason is that most hams have family members and fishing buddies who are not hams.
So ham is pretty useless for communicating at camps and family outings. 
Most hams love all kinds of radios.
 
Also, hams believe that GMRS brings people into ham radio.
So they don't see it as competition.  They see it as something that promotes amateur radio.
 
Of course there will always be some delicate egos out there.
A few guys see ham radio as a religion.
They worked very hard to get a license and don't like people who just "wrote a check".
 
I almost like GMRS better than ham sometimes because it is less exclusive.
Ham is sometimes just too quiet.
 
Vince

Hi, I'm from the HOA and we're coming for you!  Just kidding. 
 
I use the icom AH4 random wire auto tuner with my icom 718 HF rig.
It really works great with 42' of wire on 80-10 meters. 
You have to use a wire length that is not resonant on any frequency that you will be using.
You can use shorter or longer lengths depending on the bands you want etc.
 
The reason this tuner works so well is that it goes outside and there is NO transmission line between the tuner and the random wire.
The random wire feed point is right at the matching unit - and the voltage can be rather high so mount it out of reach.
This is why it needs to be an auto tuner - because it has to be mounted out at the antenna feed point.
 
It's not a cheap solution but it works very well and is very convenient.
I have no complaints about it.
 
Vince

I got my extra class ham license in 1985 and live out here in Spokane.
I often monitor the ham repeater system here that covers essentially the whole eastern half of Washington state.
I also belong to the Spokane VHF Club.
 
I find that most of the hams are surprisingly receptive to GMRS and many (or most) of them have their GMRS license.
They talk about GMRS on the ham repeater now and then.
They also have discussed it on the VHF club net and at meetings.
 
The reason is that most hams have family members and fishing buddies who are not hams.
So ham is pretty useless for communicating at camps and family outings. 
Most hams love all kinds of radios.
 
Also, hams believe that GMRS brings people into ham radio.
So they don't see it as competition.  They see it as something that promotes amateur radio.
 
Of course there will always be some delicate egos out there.
A few guys see ham radio as a religion.
They worked very hard to get a license and don't like people who just "wrote a check".
 
I almost like GMRS better than ham sometimes because it is less exclusive.
Ham is sometimes just too quiet.
 
Vince

There are quite a few "board stuffers" here in the US since it is almost totally automated.
They just load the reels of parts and set up the stencil and align/orient it.
The CAD files give all the part locations.
So there is more board assembly here than you might think.
Most of the products I designed were all built over here... with some or many foreign parts of course. 
 
Most of our low-mid volume boards were populated right in Oregon.
The blank boards themselves were more often fabricated in Asia.
Caps and resistors are almost free but the boards themselves can get expensive... $2-$15 depending on size, # of layers, etc.
 
We made educational science equipment so had all different volumes of products.
Some things were almost entirely US made and other things entirely Chinese or Thai.
It's a very complicated business.
If you buy parts in the US then send them to China for assembly and bring them back the import duties get very complicated.
You can end up paying duties twice on the same part. 
Then the finished products were sometimes sold to China and charged another duty.
So we started keeping stock in China for sales there. 
(Yes, there are American companies selling electronics devices to China.)
 
I would guess that hand held consumer radios are entirely made in Asia.
The designs could be done either here or Asia... but likely China.
The chip makers do most of the radio design since it entirely revolves around the chip for that function.
Only the support circuits (power, control, etc.) are done by the maker.
 
When I worked at Maxim (chip maker) many wafers were made in the US then tested and packaged into chips in the Philippines. 
I trained a couple of Filipino engineers in RF test back in the late 90's.
We made a lot of cell phone chips back then.
The chip designs were mostly done in the US
 
Basically, I'm just saying its a very complicated picture.
Hopefully somebody found this interesting. :-)
 
Vince

My vote for the Wouxun 805G.
 
I love the reasonably priced accessories available too.
 
Vince

If your speakers were too high of an impedance you just wouldn't get much volume.
No harm would be done to the radio.
 
If the speakers Z was too low AND you really cranked it up loud maybe you could damage the radio from excessive current but pretty unlikely.
Most audio output chips are temperature protected anyhow.
 
You could just add 4 ohms in series which should satisfy the min Z requirement. 
 
Vince

Make sure you have a ferrite or two on ALL wires connected to the car stereo.
Especially the radio antenna cable.
I'm sure it's not easy to access these things but you have to do all the wires or it won't help.
 
Vince

The Wouxun 805G is not that intimidating.
If you don't use privacy codes there is almost no setup required.
You can just use them right out of the box pretty much.
 
The bigger deal than the 5W is the antenna connector allowing use of an different antennas.
So you can put a mag mount on it for in the car or get a Smiley GMRS super stick or a Nagoya 14" flexible whip antenna.
These better antennas really do help.
They are very nice radios and I like that you can have spare batteries and switch any time.
 
If you are going to use repeaters you will want to change the display so the chan Freq is displayed rather than just channel #.
This is pretty easy.  Menu item 19 takes care of it.
 
There is no power level control so if you wan to save batteries at close range you need to switch to the low power channels.
That's about my only complaint.
 
Vince

The Wouxun 805G is not that intimidating.
If you don't use privacy codes there is almost no setup required.
You can just use them right out of the box pretty much.
 
The bigger deal than the 5W is the antenna connector allowing use of an different antennas.
So you can put a mag mount on it for in the car or get a Smiley GMRS super stick or a Nagoya 14" flexible whip antenna.
These better antennas really do help.
They are very nice radios and I like that you can have spare batteries and switch any time.
 
If you are going to use repeaters you will want to change the display so the chan Freq is displayed rather than just channel #.
This is pretty easy.  Menu item 19 takes care of it.
 
There is no power level control so if you wan to save batteries at close range you need to switch to the low power channels.
That's about my only complaint.
 
Vince