Radios dont get the distance

[rustymarlin]

Hi all can anyone help me out with some checks I can do for my 27meg and vhf I dont seem to be able to get the transmission distance out them that my mates do I regularly fish the shelf they can talk to shore base but i cant they are the exact same radios. I have replaced th 27meg aeril recently due to it breaking but this has not helped the problem And help would be great.

[TheRealAndy]

There is a few things that can affect radio transmission distances.

First is antenna design. You should have an atenna that is suited to your boat, if its a glass boat you need a ground independant antenna. An aluminium boat can have a less expensive antenna. Furhtermore, most antennas are roughly tuned. A good installer will have a tool call a VSWR meter that is used to furhter fine tune the antenna. Tuning is done by cutting very small amounts of the tip of your antenna. This cant be done with out a VSWR meter.

Second is cabling to the antenna. The cabling needs to be in shit hot condition. I often see people who cut the cable and rejoin it by soldering and twisting and using electrical tape etc. This just does not cut for radio transmissions. You need a single piece of coax all the way to the radio.

Third is the radio itself. IT needs a good power supply, no less then 12V when the radio is keyed up (transmitting). If you have had a crappy antenna, this can also cause radio problems. An out of tune antenna (can be caused by bad cabling as well) can destroy the radios transmitter output, in which case no antenna or cabling changes will fix.

I used to have all the gear needed to do this stuff, but I am pretty sure I have gotten rid of it all. I will take a look in the shed tomorrow and see if I can find any. If I have it perhaps I can help.

[oldboot]

The test instruments for 27 mhz are pretty cheep and common, but stuff to do vhf is less common & far more expensive.

Antenna choice
antenna placement

quality of all wiring

perfrmance and adjustment of both set and antenna

can all effect performance.

Start with the DC power supply cabling and importantly the quality of the earth or negative connection......
Power output in all portable radios depends on a good solid power supply.
An awfull lot of boats, trailers and automotive accessories are just wired way too light.
for the radio I'd be inclined to go direct to battery with some good red & black heavy twin with it own " best quality" breaker or fuse.


Is it a metal or plastic boat?

If it is a metal boat at some point the negative of the supply should connect to the hull somewhere..... this will give you a connection to the greater plane of earth ( the sea)..... this may provide a significant assett....then again it may not.

your coax....... the lead from the radio to the aerial........ there should be no tight bends..... tightest bend should be a radius of 2 inches....... it is very common for the excess coax to be bunched up tight & out of the way........any excess coax should be coiled in large loops at least 6 or 8 inches in diameter.......think of your coax as a pipe...... because that is eaxctly what it is.

There are aerials and aerials.......some will provide more " gain than others"... spend the extra on a better aerial......once all other things are equal..... it is the only place you can get a performance improvement.

most of the ground independent areials should come pre tuned and be pretty damn close.

someone with the proper equipment should be able to measure performance......

If you are serious you probley need to see a " radio dude".

I' make sure the basics were sorted first though, or you;ll be paying hin to do donkey work.

cheers

[FrankFWM]

Given that he has the same problem on both his 27meg and his VHF - I will take a punt that it is a voltage drop issue.

When transmitting, a lot of radio's do pull 5 amps or so... if the wire used is the wrong diameter - ie. too thin - you may have voltage drop (12v or less AT THE RADIO but 12.8 at the battery) whilst you are transmitting which would explain why both of your radios are not performing like your mates ones are...

My advice is to look at the simple stuff first before then moving on to see if you have an electrical noise problem - ie. the power wires are running in parrallel with other power wires causing electrical noise which can dramatically reduce transmitiing power or something else.

Frank

[finga]

Look for commonalities seeing the problem is in both radios just like Frank has said.
The power wire would be a good start.
The black wire would be a good second starter (only because there are usually more joins in the red wire)
Look for corroded terminals or just check all the terminals and joins (even under the insulation tape) and go from there.
Amasing how many 'wire joins' I've found in boats with two bits of wire twisted together with some tape holding it all together.

Sometimes it's just easier to just get stuck into it and rewire them and be done with it.
Fault finding can be hard to do especially if there's no definite fault.
Have fun in doing so though :)

PS If you want to get rid of any of your gear TheRealAndy (if you find it in the shed) I'd be interested in buying some more.

I lent my VSWR meter out and I think it's come back crook :-[
Yeah, I know I'm an idiot for lending. The cook tells me everytime things either don't come back or come back broken :-X

[mik01]

guys - don't want to hijack the thread but this goes with it anyway.
I installed my new vhf radio and rewired with decent wire for power and connected to the existing aerial.

on sunday at mud, I could transmit to vickie point vmr, but not hear transmissions back. after calling them on the mobile, i could hear my test vhf call came through perfectly clear but when they responded - absolutely nothing.

now I could hear both vmr at scarborough & raby bay and coastguard redcliffe etc.

should I be able to hear communications from vickie point from mud? if so, why can I now transmit but not hear if transmission requires more strength to transmit?

last question - what aerial would you then get if you wanted to replace it? whats a good quality aerial brand that covers the stuff you guys said above?

(I'm thinking I just go and replace the bloody aerial and that should fix it?)

cheers,
Mick

[finga]

replace the aerial matey :)

[mik01]

replace the aerial matey :)

yeah thanks Scott ;) - figured it would be the issue.

can you recommend a good quality one - price isn't really an issue - just want to make sure I am covered out there.

cheers,
Mick

[Quirky]

Mik01,

if you are anywhere near the Gold Coast City Marina drop in and see EMS (Electronic Marine Solutions). They are distributors/importers for Glomex antennas, the 5' VHF antenna is excellent, they also sell swivel mounting brackets to suit. From memory the antennas are about $50, the mounts somewhere around $25. These antennas are pretuned, just fit the supplied coax connector and away you go.

[deek]

You could try Moonraker aerials at moonraker.com

[fishingrod]

RustyMarlin,
If your around Berowra-Carlingford in Sydney, I can help with a VSWR meter and volt meter. Ive got a VSWR meter that covers 27meg and up to VHF/UHF and can help identify the other issues.

Re Mic01 question re antenna brands.
Ive used the GME AE30, GME AE87 and Navman 2.5m version with good reliable results. I dont have a lot of faith in the MobileOne brand from Dick Smith.

cheers
Rod

[finga]

I have a Navman one and am happy.
I suppose any pretuned name brand would do the job.
Ring around though as the price varied from about $80-$150 for the same aerial.
I ended up getting one from Yatala Marine (I think it was :-/). Not repeat NOT
the place closest to the highway but the place next door where you can buy a new boat/motor

[trueblue]

Go to Commex communications in Newmarket. They have their own antennaes. Take the boat and let them size the antennae to suit things like the bimini etc.

They will tune it all up and also radio test via the ch 81 repeater.

word of warning though. they are in a tight parking area. call them just before you arrive and check that you can drive in straight up the drive way and then back the boat into the shop - otherwise you could get caught in a very tight spot.

great service from them.

Cheers

Mick