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W9DSD
09-13-2011, 12:48 PM
I'm looking for cable recommendations for a mobile install. I'm mounting a 1/4 wave dual band antenna on the driver's side rear stake pocket of my truck. I'm going to route the cable along the frame where it exits the truck bed, and through the firewall into the cab, probably about a 15' run.

Which type of cable will be the better one for this install, considering that it will be exposed to moisture under the truck? Thanks for your help.

W1VT
09-13-2011, 12:56 PM
I'd suggest a cable designed for direct burial, such as Times LMR-195-DB or LMR-240-DB.

K0BG
09-13-2011, 01:33 PM
You really don't need any coax larger than RG8X. The lengths are short, so the difference in loss is just a few tenths of a dB. Any decent grade is just fine. The JWC RG8X sold by AES, and HRO, is just fine. And, there is another related issue, especially when operating HF.

Almost without exception, most mobile installations end up with some common mode current. If you're careful, you can get 7 turns of RG8X through a 3/4 inch ID split bead. You end up with a CM choke of about 2kΩ at 10 MHz, and the impedance is mostly resistive, which is what you should strive for. If you were to duplicate the choke using RG8 sized coax, you'd need 49 ferrite cores. The cost differential is obvious.

KF5FEI
09-13-2011, 02:09 PM
If you are going to do 2m and up, go with LMR-240. 58 and 8X can be lossy at higher frequencies, even with short runs.

W1GUH
09-13-2011, 02:31 PM
Practical suggestion -- get your coax jumpers from someone you know to make good ones or make them yourself. Me and a friend have wound up with jumpers that went bad (opened up somewhere) pretty often. And I gotta tell ya...a bad coax jumper can drive you up a tree -- can appear like something awful has happened to the antenna!

Rule of thumb....

If your antenna (fixed or mobile) seems to go bad "all of a sudden" check the coax connections FIRST!

Have fun!

N4EYZ
09-13-2011, 03:36 PM
I ran 8x for hf and 2/440 to my 706 for over 10 yrs with never a problem. Ran under the truck too. Do it and don't worry about it.

Wayne/n4eyz

K0BG
09-13-2011, 06:21 PM
RG58 perhaps, but RG8X is better than most folks realize. If you just have to have lower loss UHF cable, then RG223 is the way to go. You'd best sit down for the price, however.

WB0LSR
09-13-2011, 07:06 PM
I'm with the LMR240 suggestion, although I'm not practicing that myself right now. My dual-band setup is running a short run of RG-58 presently, I've not had any real issues with losses, at least not according to what I measure at the antenna. LMR-240 has very low loss at higher frequencies, with better performance than 8X with the same diameter. It is a tad more expensive though.

K9STH
09-13-2011, 08:19 PM
Frankly, in a mobile installation, and especially with FM, you will not be able to tell the difference between RG58/U, RG8/X, LMR-240, or even LMR-400 or LMR-600. You are going to lose more in the connectors than what you can lose in 10 to 15 feet of cable.

Now if you are running mobile E.M.E. using CW or SSB, then you "might" see a difference and even then it is going to be so small that it won't make any difference unless you are operating in the SHF region!

Glen, K9STH

KC9SQR
09-13-2011, 08:35 PM
If the antenna is being put on your truck for general local and repeater work, I'd just run the rg-58 and be done with it... That's what I've used for a while with results I can't complain about... As long as the coax run is short like 10-15 feet, I don't think you'll have any issues...

Using my HT through about 12 feet of rg-58 I can get into the "255" from about 30-40 miles away :)
I'd think that sticking a decent antenna with 3db or more of gain on the roof should offset any losses from the coax... But I'm only going by personal experience with my own setup...

73
Will

K7JEM
09-13-2011, 08:46 PM
RG58 perhaps, but RG8X is better than most folks realize. If you just have to have lower loss UHF cable, then RG223 is the way to go. You'd best sit down for the price, however.

RG223 loss is virtually identical to RG58 loss, if the cable has a solid center conductor. RG8X has a lower loss than the smaller cables, like 223 and 58. Foam dielectric and solid center wires can sometimes be a problem in mobile installs, but usually not.

As Glen says, for short runs in mobile low and medium power, RG58 is fine. RG223 would work good for very high power HF or VHF. The silver plating and Teflon help out at those high power levels, but not any advantage below 400 watts HF or about 200 VHF or so.

Joe

K0BG
09-13-2011, 09:19 PM
I TDRd the RG223 I purchased from General Cable several years back, and the spec were almost identical to RG303. The ARRL Handbook agree with you, Joe.

This brings up an interesting subject. Just how good are the coax cables we buy?

I think we all tend to read the data sheets, but that isn't necessarily a good indicator. Years ago, when I worked for American Radio, we tested a batch of RG213 cable assemblies made by a company in Hong Kong. The samples we got were superior to samples of RG213 made here in the states by Belden. Subsequent examples proved to be no better than RG58! I don't suspect its any better today.

K7JEM
09-13-2011, 10:10 PM
I TDRd the RG223 I purchased from General Cable several years back, and the spec were almost identical to RG303. The ARRL Handbook agree with you, Joe.

This brings up an interesting subject. Just how good are the coax cables we buy?

I think we all tend to read the data sheets, but that isn't necessarily a good indicator. Years ago, when I worked for American Radio, we tested a batch of RG213 cable assemblies made by a company in Hong Kong. The samples we got were superior to samples of RG213 made here in the states by Belden. Subsequent examples proved to be no better than RG58! I don't suspect its any better today.

It's hard to imagine 213 being worse than 58, unless there is something seriously amiss with the 213. Did you find any reason for it?

Generally speaking, foam has lower loss than solid, solid center has lower loss than stranded center, and larger diameter has lower loss than smaller diameter.

Siver plated vs. copper is about the same. Teflon vs. solid polyethelene is about the same. The silver and teflon help out for heat durability, as in high power. Silver and double shielding help out in repeater installations, or where max isolation is needed. For the most part, the shield coverage is of little importance in loss caculations. I think the difference between double shield, 98%, 95%, and 80% coverage is minimal as far as losses go.

New coax is generally better than old coax, other things being equal. Dry coax is superior to coax with water in it. :p

Joe

WB2WIK
09-13-2011, 10:57 PM
Dry coax is superior to coax with water in it. :p



Now you tell me.

KG6UTS
09-15-2011, 07:22 PM
RG58 perhaps, but RG8X is better than most folks realize. If you just have to have lower loss UHF cable, then RG223 is the way to go. You'd best sit down for the price, however.

223 is good stuff alright. I used that and RG142, same connectors, because I found rolls of each surplus along with a 500ft spool of Comscope RG6. RG142 can carry some power for its size.

EdZ KG6UTS

K0BG
09-15-2011, 09:31 PM
Joe, bad coax just happens.

I remember when I was working for CW Electronics, the owner bought a bunch of remnants from Columbia Wire & Cable. Some of the longer lengths we cut to 50 or 100 feet, installed PL259s, and sold them as assemblies. All said, and good. But a bunch of the remnants were a result of requisite splices during manufacturing. Most of the time, the shield was missing for a few inches, but sometimes it was the center conductor. I learned an obvious lesson from that experience.

W9DSD
09-16-2011, 07:34 PM
Well, i got the coax run and the mount is grounded to the frame rail. Now my issue is the SWR. I'm getting a 1.1:1 a 5W, 1.3:1 at 10W, but when i step up to 30W (Yaesu FT-2900), the SWR is over 2. Any thoughts??

I used RG58 at 25 feet. The antenna is a 1/4 wave 2M/70cm whip on a stake pocket mount on the rear of the driver's side. I'm thinking it's where it's mounted, but i should be able to put more than 10W into it.

K0BG
09-16-2011, 08:42 PM
My first question is, how are you measuring it? If you're using the one built into the transceiver, all bets are off.

W9DSD
09-17-2011, 01:46 AM
My first question is, how are you measuring it? If you're using the one built into the transceiver, all bets are off.


It's a Yaesu FT-2900, just a simple 2 meter rig....no meter built in

K0BG
09-18-2011, 12:08 AM
Some may disagree, but internal SWR/power meters are all but worthless! If you really want to know what's going on, you need a calibrated wattmeter like a Bird 43 with the appropriate slug. An alternative is an antenna analyzer, like the MFJ 259B. Either of these will tell you much more than any internal (or infernal as the case may be) meter.

W9DSD
09-18-2011, 08:35 AM
Some may disagree, but internal SWR/power meters are all but worthless! If you really want to know what's going on, you need a calibrated wattmeter like a Bird 43 with the appropriate slug. An alternative is an antenna analyzer, like the MFJ 259B. Either of these will tell you much more than any internal (or infernal as the case may be) meter.

If you don't have an answer for my question, then please do not respond at all...I have no idea what the above comment has to do with my original question...As i stated in MY previous post, there is no internal meter...I'll post this one more time, and hope for a more intelligent answer...Please do not refer me to your website again, as you have done in previous replies, because it doesn't seem to have all of the answers either...

"Now my issue is the SWR. I'm getting a 1.1:1 a 5W, 1.3:1 at 10W, but when i step up to 30W (Yaesu FT-2900), the SWR is over 2. Any thoughts?? I used RG58 at 25 feet. The antenna is a 1/4 wave 2M/70cm whip on a stake pocket mount on the rear of the driver's side. I'm thinking it's where it's mounted, but i should be able to put more than 10W into it."

K9STH
09-18-2011, 03:25 PM
It sounds like your SWR bridge is having problems. Is it designed for VHF? If not, then all bets are off. Something like a "CB" SWR bridge or one designed for amateur radio HF operation will give an indication but it will only be relative. That is, it will indicate when the SWR is lowest but the actual reading will be meaningless.

The actual SWR does not change with power levels. However, especially with a "moni-match" type of SWR bridge that is designed for lower frequency use, the readings will not be accurate and the readings will be all over the place as you increase power. The "pickup" should not be any longer than about 10 percent of the actual wavelength of the signal and 5 percent or less is considerably better.

25 feet of RG58/U is a "bit" long on 440 MHz. Most mobile installations use between 10 and 15 feet. One thing that may be happening is that with the longer length the attenuation is such that the reflected power may be at such a level that the diodes in the SWR bridge are not conducting enough at the lower power and therefore the voltage reading does not reflect the true reading. Remember, with enough feedline length a "perfect" match will be seen at the transmitting end even though the actual SWR of the antenna may be astronomical. In that case, you have to measure the SWR right at the antenna to get the real reading. I suspect that the actual SWR of the antenna is a lot higher than what you are reading on 440 MHz at the transmitter end.

Now using something like a Bird 43 (I have a Bird 4305) will generally give a more accurate reading. However, if all that you are looking for is the best match then just about any SWR bridge designed for the frequency range will work.

Glen, K9STH

K7JEM
09-18-2011, 03:42 PM
If you don't have an answer for my question, then please do not respond at all...I have no idea what the above comment has to do with my original question...As i stated in MY previous post, there is no internal meter...I'll post this one more time, and hope for a more intelligent answer...Please do not refer me to your website again, as you have done in previous replies, because it doesn't seem to have all of the answers either...

"Now my issue is the SWR. I'm getting a 1.1:1 a 5W, 1.3:1 at 10W, but when i step up to 30W (Yaesu FT-2900), the SWR is over 2. Any thoughts?? I used RG58 at 25 feet. The antenna is a 1/4 wave 2M/70cm whip on a stake pocket mount on the rear of the driver's side. I'm thinking it's where it's mounted, but i should be able to put more than 10W into it."


You need to answer a simple question that has already been posed. What are you using to measure SWR?

Most simple SWR meters may be inaccurate at VHF and/or UHF. That is why it is important to know what you are using.

SWR will (typically) not change due to variations in power, that is the problem I see here. IF you are getting variations, it is most likely something in the equipment you are using, or not properly calibrating or reading the meter. The antenna itself really has no way of changing SWR on its own. It doesn't know the difference between 5 watts and 30. And a QW antenna will usually have acceptable SWR if it is cut to the right length.

So, you need to answer the question. What is the make and model of your meter? Are you calibrating it each time you change power? What frequency are you checking it on? Is it a QW on 2M or 440? What is its physical length? What brand and model?

Joe

W9DSD
09-18-2011, 09:02 PM
The meter i'm using is an MFJ844 and i'm testing at 146.000...Sorry if i seem a little stand-offish, i'm just a little frustrated with what's going on with this antenna. I have the same exact whip on a mag mount with about 15 feet of RG58, and 1.3:1 is the highest reading i get with that antenna.

KG4NEL
09-18-2011, 09:29 PM
Have you tried it with a different run of coax?

W9DSD
09-19-2011, 12:59 AM
Have you tried it with a different run of coax?

I have not tried a different run of coax. The length i have was purchased new from a local electronics distributor, and soldered the connectors on myself. The previous comment by K7JEM in reference to SWR not typically increasing with an increase in power has me baffled, because this has been the norm on other antennas i have tested. My rig, a Yaesu FT-2900, has power settings of 5, 10, 30, and 75 watts, an my other antennas read nearly flat on 5W, and a maximum of 1.3:1 at 75W.

I suppose it's entirely possible that i got an inferior piece of coax from the supplier, but i won't know for sure until i try another piece. It may be overkill, but i may pick up a chunk of LMR-400 and run that instead. Another couple of details...I ran a ground wire run from the mount to the frame, thinking that might help the situation and it did not improve anything.


Regarding the cable routing, i ran it along the top of the frame rail, into the engine compartment, and through a grommet in the firewall, which is why i needed the 25 feet. When i key up at 30W, the signal completely drowns out an FM radio i had playing in the garage, about 40 feet from the truck, which was outside in the driveway. I don't know if this sheds any light on the situation, but i'm still open to suggestions.

K9STH
09-19-2011, 04:30 AM
It says that the FM radio has very poor selectivity, especially in the front end! However, this is true of most of consumer products on the market!

Is the frame rail actually connected to the rest of the vehicle? Many times there is paint between the various components of a vehicle and a good connection is not being made.

What type of mount are you using on the antenna? How is it connected to the frame rail? This can have a very adverse result if the mount is not properly grounded.

Glen, K9STH

K7JEM
09-19-2011, 05:04 AM
That meter is not a really good meter, it is probably adequate. It has no way to calibrate for SWR, so your readings will be relative only, not a true indication.

Check the SWR at 144.2, 146, and 147.9 or thereabouts. Check them on the ten watt level, then let us know what it is at those different frequencies. The SWR isn't changing, the meter is giving you funny readings.

Joe

W9DSD
09-19-2011, 07:49 AM
STH,
I am using a stake pocket mount on the rear driver's side of the truck. I ran a 10ga. ground wire from the mount directly to the frame of the vehicle, which i used a dremel tool to expose the bare metal for the grounding connection.


JEM,
I checked the SWR at 144, 146, and 148. The SWR is reading the same at 5W throughout the band, it only fluctuates as transmit power is increased.

K7JEM
09-19-2011, 02:36 PM
STH,
I am using a stake pocket mount on the rear driver's side of the truck. I ran a 10ga. ground wire from the mount directly to the frame of the vehicle, which i used a dremel tool to expose the bare metal for the grounding connection.


JEM,
I checked the SWR at 144, 146, and 148. The SWR is reading the same at 5W throughout the band, it only fluctuates as transmit power is increased.

The 5 watt level will be the most inaccurate way to check, using that meter. It really isn't an SWR meter, it looks at forward and reflected power, but the SWR scale is only accurate at full scale forward power, if it is accurate at all. You need to look at a forward power level that will give you as close to a full scale reading as possible. 5 watts will always be low, and very inaccurate.

What is probably occurring is that the 3/8-24 mount you have is adding additional length to the antenna. How does it connect to the feedline? Is there a PL259 connector on the bottom of the mount, or does it use stripped ends of coax with ring connectors? Can you get us a picture of how the coax attaches to the antenna?

A 3/8-24 antenna for 2M and 450 is a pretty poor choice. Those mounts were designed for HF, where they work well. At VHF and above, the only (and I do mean only) mount used by professional 2 way people is the NMO. The only people using 3/8 mounts are hams, and for good reason.

You probably have relatively high SWR on the antenna, but it doesn't manifest itself at low power, due to the construction of the meter. Your coax itself is probably OK, I would suspect how it attaches to the antenna. A picture of that would help, along with SWR readings at top, middle and bottom of the band, taken at 10 watts and 30 watts or whatever.

Joe

W1VT
09-19-2011, 02:47 PM
http://www.eham.net/reviews/detail/5073
N6YB explains that in the "SWR" mode, the meter actually measures reflected power with an X2 multiplier.

Thus, if it reads 10 watts(using the power scale), you actually have 5 watts reflected power. He suggests calculating SWR based on the ratio of reverse to forward power.

K7JEM
09-19-2011, 03:39 PM
http://www.eham.net/reviews/detail/5073
N6YB explains that in the "SWR" mode, the meter actually measures reflected power with an X2 multiplier.

Thus, if it reads 10 watts(using the power scale), you actually have 5 watts reflected power. He suggests calculating SWR based on the ratio of reverse to forward power.

Yes, that is the way to do it. The SWR scale is only accurate when the forward power is full scale, which it rarely is, and never in this case. The power scale is better to use, as the calculation can be made better that way.

Joe

K7JEM
09-19-2011, 03:54 PM
Here is another quick test. May require two people. Key a 25 w signal into the antenna, and while watching reflected power, have someone bring their hand toward the bottom part of the antenna rod. Start from about two feet away and slowly move your hand toward the base, while you watch the SWR. If the meter starts going up as the hand approaches, your antenna is too long. If the meter starts going down, and either continues to go down, or hits a dip, then starts increasing, your antenna is too short. If you see no change, your antenna is not radiating.

Don't touch the antenna! You don't need to get closer than about 3 inches or so.

Joe

K9STH
09-19-2011, 06:43 PM
Unless the ground wire is VERY short, it can be introducing problems into the performance of the system. Stake bed installations are notorious for grounding problems.

Although for lowband installations (46 MHz range), the old Lone Star Gas Company used to install full quarter-wave whips on top of stake bed racks. Unfortunately, they had all sorts of problems especially when the trucks were in motion with breaking up, etc. The "cure" for this was to install a short piece of braid from one of the mounting bolts of the "ball mounts" to the cab of the truck (less than 6 inches which would equate to less than 2 inches for 2-meters). This single "trick" resulted in the company stopping to use their "old" radio service company and giving the service contract to the company that I owned. Several previous contractors had not been able to "solve" the problem! This was back around 1980.

Glen, K9STH

W9DSD
09-19-2011, 09:33 PM
Well, thanks for all the tips and advice. It was greatly appreciated. I thought maybe the coax was junk, so i disconnected it and installed a 12 foot jumper from the rig to the antenna. Same exact issue as before. I guess the stake mount is just a s%#@ way to go about it for UHF/VHF, so i will resign myself to the use of mag mounts. I have about 3" if i'm lucky between the roof of my truck and the garage door, so i don't see any other options. A permanent roof mount is out of he question with the clearance i have. Thanks again.

W1VT
09-20-2011, 01:47 PM
Too bad nobody has invented a mobile antenna that will get out of the way of garage doors and other obstacles.

WA7NXI
09-20-2011, 04:46 PM
You need to install a permanent NMO mount in the roof of your truck and then use a genuine motorola QW stainless steel whip unity gain antenna....they are extremely tough and can handle getting bent 90 degrees right at the base all the time to clear garage doors, etc. Most police/fire vehicles use these antennas just for that reason, it's what I use on my Nissan truck and it has been beat to holy heck for years and it's still working great....plus they are very inexpensive compared to the fancy Diamond/Comet antennas avail on the market. Good luck.

KF5FEI
09-20-2011, 06:43 PM
We use the generic dual-band NMO mount 1/4 wave antennas on roofs of our cars with clearance problems -- works well and they are $12-14 at most hamfests. Palmetto Antennas usually has them, but other vendors sell them too. On the road we swap them out for the cheapy dual-band 5/8 wave antennas for a bit more range.

K0RGR
09-20-2011, 07:04 PM
It's pretty unlikely on VHF/UHF, but there is a small chance that your rig is 'taking off' and producing a spurious signal somewhere that the antenna does not perform well. It's probably just a coincidence that you're wiping out an FM radio nearby, but it could also mean a spur somewhere near the FM band. Try adding another piece of coax in series with the one you have - make it a bit longer. See if that changes things. It's possible that you just have a peculiar mix of reactances at that particular frequency, with that length of cable.

I think I agree on the stake bed mount. I would think it would be tough to make this work on VHF/UHF. I've used 3/8 mount antennas on 2 meters but not on UHF.

K4LMP
10-24-2011, 08:54 PM
I am using a bed stake mount on my dual bander with no problems. I am running about 20 feet of RG-8X coax. For grounding, I ran about 6 feet of #8 wire to an existing point under the truck where a bunch of ground connections are tied to the frame. I used an MFJ antenna analyzer to adjust the antenna. With the antenna as short as possible, the SWR was 1.2 at 146 Mhz, and about 1.8 at 148 MHz, so I left it alone and didn't mess with it anymore. I can get into any repeater in my area. Here is my antenna http://www.jetstream-usa.com/jt7905b.shtml and here is the mount I am using http://bellsouthpwp.net/b/r/breedlove1/page34.html go down and to the left to the Heavy Duty Side Stake Pocket Bracket. $45 and the best you can get. I also used http://bellsouthpwp.net/b/r/breedlove1/page33.html the picture on the top left, with the brass nut. I have no problems and can hold the mount and shake the whole truck with no movement at all (3500 1 ton 4WD crew cab dually with diesel). I highly recommend Breedlove Machine Shop for quality mounts.

W9DSD
10-30-2011, 05:48 AM
I've been giving my issue with SWR a lot of thought, and i think i'm gonna swap out the RG58 coax for LMR400 and see what happens. I have some extra laying around, and at this point i have nothing to lose. I think i may have gottten some crappy coax. It's the one thing i haven't tried yet. I'll use a short piece of something a little more flexible once i get into the cab and see if that improves the situation.


K4LMP,

What kind of power are you putting through your mobile??

K0BG
10-30-2011, 01:59 PM
There is no reason to swap out the coax. The difference in power reaching the antenna won't increase more than about .25 dB. In fact, there is a reason not to. No matter the install, there is always some common mode current flow. Choking RG58, or RG 8X requires just one split bead with 7 turns. Equaling that with LM400 will take 49 split beads. As for power? Good quality RG8X will easily handle legal limit if the SWR is reasonable. With just 500 watts, RG8X will handle even 10:1, so the question remains; what perceived advantage do you think you'll have?

K4LMP
10-31-2011, 11:43 AM
Dave, the power depends on where i'm at and what repeater i'm trying to get into. The radio is 50w on 2m and 35 on 440. I think in memory, I have most set at about 25 watts. I checked my swr with the analyzer, and all was well. I did check the reflected power on my meter, and it was minimal, not enough to worry about.

Jeff
K4LMP

W9DSD
11-03-2011, 05:23 AM
so the question remains; what perceived advantage do you think you'll have?

You said it yourself in a previous post, where you stated that "bad coax just happens". I have nothing to lose by running the heavier cable. I have no clue as to the manufacturer of the current coax i'm using, other than the fact that it's an imported cable, and as a result, may very well be s@&!. It appears to be aluminum with a stranded center conductor.

So, i am going to run the LMR400 just for giggles, grins, and the fact that i have nothing else to do tomorrow on my day off. I'll let you know how it turns out. I'm betting that the new cable will drastically improve my situation, and if not, at least i can say i tried.

The antenna will primarily be used for 2M work, local repeaters as well as simplex. The 70cm end is primarily for use with the HT. Thanks for the advice.

K7JEM
11-03-2011, 07:04 AM
The chances that it is the coax is very slim, especially since you already tried it with another piece. Your problem is most likely the antenna is too long, or the mount is giving issues. You never ran the simple SWR tests at various frequencies, so we really don't know. 20 minutes of troubleshooting and measuring trumps an hour of shotgunning.

LMR400 is a poor choice to be using in a mobile setup, just makes no sense. But you will do what you want, makes me wonder why those of us that have tried to help even responded in the first place. There just isn't much to go wrong with a piece of coax. Check it for physical issues, check for shorts or opens, and it should be OK. Connectors are more often the culprit on coax cables, rather than the cable itself. We can only assume those were put on right.

Joe

K0BG
11-03-2011, 01:30 PM
I have had bad coax cable several times. That is why I won't purchase any more cable made by Coleman. What I use now came from AES (http://www.jscwire.com/jsc_ss.taf?p=3062) I've used about 200 feet of it off a 500 foot reel, and have had no problems. The best part is, it is made right here in the good old USA!

KG6UTS
11-08-2011, 04:00 PM
I used RG-141 on the Jeep mobile, short runs and same size as RG58 but better shield etc. It was purchased surplus.

EdZ KG6UTS

KB0MNM
01-05-2012, 03:17 AM
Dave- See page 48 of the September 2010 QST magazine. W1ZR rates Belden 8259 (RG-58) for 2.2 dB per 16 ft. at 440 Mhz. Unless you want to waste a lot of money with hardline, this is the result that should be acceptable. I suspect that the 1/4 wave is not exactly correct- depending on which band. This post is devoted to my old associate Steve ( NAS )- who may not have been thinking about the reaction at higher frequencies. But then things do get warm in Arizona. 73-

KB0MNM
01-05-2012, 03:36 AM
Dave- You also mentioned moisture under the truck. This is something that you probably cannot escape. The real problem is all of the tiny little rocks that might hit the coax. Consider using a product like "convoluted loom tubing". This is something that can be purchased in many automotive stores ( at a rather large price per foot ), or through some trade suppliers. It is generally black and often called "Split loom". There is no problem with moisture nor even salinity from the roads if it cannot enter the cable shield. Use a good tape ( like 33+ ) if you want no repeats. 73 - Jon

AD5MB
01-06-2012, 01:19 AM
W9DSD, have you read This web page about mobile radio installations? (http://www.k0bg.com/)

I am an electronic technician since JFK was in office and an electronics instructor since Richard Nixon lived in government housing and a tech writer, and I am awestruck by this web page

forget split loom - use spiral wrap. much thicker, stands up beter to UV and ozone, you don't have to use tie wraps to keep things in.

KB0MNM
01-10-2012, 04:12 AM
Dave- I think that AD5MB does endorse protecting the coax, but am not sure which spiral wrap ( there are a few ) that he has in mind. The 'split loom' that I refer to is sold by various commercial outfits which should be convenient: WalMart has the stuff for about $3.99 in the electrical section next to AC distribution strips- this is a little high for 6 feet of 1/2" or 3/4" size stuff. You can find a similar price at O'Reilly / Checker auto parts without looking so hard. Tessco (www.tessco.com (http://www.tessco.com) ) sells it in 50 ft. lengths and you may be able to resell some later- or not. In any event, protect the coax from abrasion for longer life. KB0MNM(/5)-73

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