Expect 27mhz range in moreton bay ?

[datamile]

Hi,

I've got a gme gx294 with a tuned ae60 ( 1.8 m) aerial, but I hardly hear anything in the bay on channels 88/90.

What sort of range should I expected if the setup is working, and are there busy channels that I should be able to pick up on ?

Anything I should check if I should be picking up traffic ?

Thanks

[Kleyny]

i get maroochy vmr in at the cockle banks. i can also get brisbane vmr.
Mine is just a uniden with a 1.8m aerial mounted on my consol so its roughly 2.5-2.7m off the water.

neil

[liltuffy]

Mate, try some other channels like 91 or 96. 88 in particular is the emergency channel which as it states should only be used in emergency

[QF3 MROCP]

Mate, try some other channels like 91 or 96. 88 in particular is the emergency channel which as it states should only be used in emergency


Print this out and laminate it. Then stick it next to your radio. You might also write your boat rego on it for when the VMR asks you for it when logging in and out.

Around the bay you should be able to get a VMR on 91 or 90. If you're on the eastern side of the island - maybe not - although you could try 91 with some luck.

Why not spend some extra money and get a VHF unit.. the coverage and audience is wider, especially for distress help...

Peter

[datamile]

Got that sticker already. Just thought the radio or aerial might be busted due to lack of reception, I'll listen out on other channels and see if I get anything.

Normally out of vicky point, and range from peel to jumping pin.

[QF3 MROCP]

Mate, try some other channels like 91 or 96. 88 in particular is the emergency channel which as it states should only be used in emergency


liltuffy:

88 & 86 are known as calling channel channels for distress, urgency and safety calls. As a calling channel, they can therefore be used to make initial contact with a VMR or another ship. Once contact is made, you then transfer over to a working channel eg, 90 or 91 (I've never heard of 96 being used?).

Peter

[QF3 MROCP]

Got that sticker already. Just thought the radio or aerial might be busted due to lack of reception, I'll listen out on other channels and see if I get anything.

Normally out of vicky point, and range from peel to jumping pin.

also check your microphone connection to the radio unit itself. (especially if it one of those that screw into a socket) there is a wiring relationship with the aerial circuit.

If you are testing it from Vicky Point, then the local VMR should be able to get you. Give them a phone call first and line up a time with their radio room to try all 27Meg channels they monitor....

[walruss]

If you doubt your aerial try and find a SWR meter (single wave reflection) and test the aerial to check that it is tuned correctly. Its unlikely but a possibility. Most two way communications places will have one. If a removal aerial it may be as simple as not screwed all the way to the bottom.

Russ

[MTAQ/BTAQ]

Correct me if I am wrong - I thought there was 27mhz "repeater" on Moreton Island which solved many of the 27mhz problems.

Mind you I use VHF for I have found that 27mhz will let you down when you need it (that wet windy day when Murphy has it in for you)

[wags on the water]

I have contacted the radio room at MBTBC from the 35's and 42's off Moreton earlier this year with the 27meg.

[oldboot]

From what I gather 27 Mhz can be pretty quiet, even on weekends.

I agree that VHF would be a better option.

I do not believe there are any 27Mhz repeaters in SEQ..... correct me If I am wrong..... even then to use a repeater your set would have to have a specific feature available and enabled..... I don't know that many 27 meg sets are set up for repeaters.

You should know if it is working if you log in.


Push comes to shove .. I have a set of meters for 27 meg..... at least with a set of metters you can establish that you are.
Transmitting and at how much power.
you are modulating.. your microphone is working.
your SWR within spec.........you antenna is OK.

any of the vmr radio rooms should be able to give you an on air radio test.

cheers

[charleville]

If you doubt your aerial try and find a SWR meter (single wave reflection)



Not really meaning to be picky but people who search on this might misunderstand.

SWR is Standing Wave Ratio.

Way back when I was a working person, I knew lots about SWR but now all I know is what it stands for. ;D ;D ;D

Fundamentally, it is a bit like what happens at an ocean bar. If there is no major difference in conditions along the transmission path of a signal from the radio transmitter into the antenna cable and into the antenna, all is hunky dory and the signal finds its way out into the atmosphere with minimal signal strength loss and with no damage to any equipment (eg the radio itself) along the way. Likewise, if the Southport Seaway is well dredged and deep, boats can come and go from the open ocean to the smooth water without any hassles.

However, if there is a difference in the "impedance" between any components then there will be reflections in the signal back from that impedance back towards the radio. "Impedance" is a flash term that technical guys understand but allow me, if you will, to continue with the ocean bar analogy.

ie If there is a sand bank at the entrance to the Seaway, then there is not a smooth transition and the waves will stand up - ie we have standing waves. This is where the analogy must end because what happens in the radio set-up is that when the electrical signal hits that 'sand bank', some of it is reflected back to the source, ie the radio.

In the worst possible case, the magnitude of these standing waves may be large enough to blast the guts (another technical term ;D ) out of the radio but more often, the 'damage' will be just that not all of the signal is getting through to the antenna - and vice versa from the other direction - so that you will not transmit as much power into the atmosphere nor will your radio "hear" as much of the received signal coming in.

The impedance of an antenna varies with the frequency of the signal. Impedance will also be affected if the coaxial cable feeding the antenna is crushed at some point or there is a bad connection or probably fifty other reasons.

I would think though that if you have a standard radio into which you plug an antenna which suits that radio (ie 27 MHz or VHF) and which is hard wired to the antenna cable, and you have not damaged anything, it all should work without drama. Having said that though, whilst I have tons of experience working with SWR type issues, I have never worked with marine radios so I am quite happy for anyone with hands-on expertise to tell me that whilst my explanation is correct, issues can happen with standard installations, if that is the case. :)

[oldboot]

pretty much on the money charley.

SWR is the standing wave ratio as you said. it is the ratio of signal that is sent to the antenna feed line and the amount that is reflected back....

I good SWR will indicate that the feeder ( that is the cable) is connected to something that precents the correct impedance and there isnt anything upsetting the process along the way.

If you have an SWR of 1.1 to 1 which is pretty good for mortals, you are getting about 90% of your energy to the load ( the antenna).

if you have a poor SWR say 2 to 1 this means you are getting 50% of your energy to the load and 50% comming straight back at you... this isnt good.
Any radio with protection circuits in the output stage will shut down at this sort of level.
lots of radio systems run at 1.2 to 1 or even 1.3 to 1.
you can realy have a lot of power going missing if your radio system isnt running sweet.


most of the marine antennae.... especilay the ground independent antennae are pretuned and there realy isn't much to you can or have to do except install as per instructions.
It is impoprtant that you do not shorten the cable on any of the ground independent antennae.....as they need a specific length of cable (or more than certain length of cable) to work properly.
This is to do with the jiggery pokery they do to make a ground independent antenna work.

cheers

[charleville]

A multiplicity of thanks, Aged Footwear. :)

I have probably taken the thread on a bit of an unnecessary tangent to the original question but the pedant in me felt a need to clarify the use of the term SWR.

As I said, many years ago, I had tons of experience in dealing with SWR matters but on a different scale to production type marine radio equipment. Your clarification of the practical matters in relation to production quality radios, especially your last paragraph is very useful. Many thanks.

Coincidentally, having just blown up my second 27 MHz radio in seven years, probably because I never bother covering the boat, nor closing the canopy and protecting it from rainfall. I suspect that moisture has done its malicious deed again. So I have just bought myself an Icom VHF radio and accordingly I am due to install that and a new antenna, myself, before my next trip. I feel completely naked without a working marine radio. :(

My only annoyance now is that all antennae seem to be white in colour. This is a dreadful nuisance for someone who has a runabout with the antenna located in front of the helm and who likes to fish at night. The reflection of light off a simple vertical antenna thus causing a hindrance to night vision is a nuisance so I guess that I shall have to cover this one in black insulation tape like I did with the old 27 MHz antenna.



.

.

[oldboot]

Charlie .. charlie... charlie.... at least heat shrink please8-)


you would be wise to invest in an oil container.........cho the side ir top out of an oil container & drop it over your radio......

Oil containers last much better than icecream containers.

cheers

[charleville]

Charlie .. charlie... charlie.... at least heat shrink please8-)



Heat shrink - Yes!8-) Never thought of that. :-[

A multiplicity of thanks. :)



.

[garman1]

Charlie, what about a can of spray paint................. couple of coats (not to thick) and bobs ya uncle....................

havn't had much to do about SWR since I had my ham radio shack, yeeeaarrrs ago

[oldboot]

the problem with spray paint is that it wont stick well to the surface of the aerial without some " preparation".

a couple of sections of adhesive lined heat shrink & it should just about out last religeon. tw different sizes of shrink would be the go to allow for the taper and join them just above the loading coil.

cheers

[TheRealAndy]

Could I go super techy and give you the real explanation of SWR;D

I was unfortunate enough to do a shit load of RF type stuff when I was at uni (plus I am an old HAM) and we even had to apply the theory to computer motherboards!

[garman1]

Hey Andy we"ll have to catch up for a chat on cw............. been 20 years since I chatted using morse code................. Ah the glow from the finals of a yaesu ft 102 and the warmth from the yaesu FL2100 .....toasty..........!

It's been a long time since I built a beam or made a quad as well ... ah memories

[TheRealAndy]

Hey Andy we"ll have to catch up for a chat on cw............. been 20 years since I chatted using morse code................. Ah the glow from the finals of a yaesu ft 102 and the warmth from the yaesu FL2100 .....toasty..........!

It's been a long time since I built a beam or made a quad as well ... ah memories

I doubt I could tap out any morse these days. I got my licence at 15 and I was hitting about 15wpm under some old navy guy. As for yaesu, pfft, at 15 I had to build it!! My pride was a 2m Dick Smith kit that had a digital LED readout! The rest of my gear was modified CB radios for 10m. Thing is, once I got my kit all working I quickly learned it was all about people trying to contact people as far away as possible, rather than building gear. I lost interest quickly after that.

[garman1]

I know what you mean, I had a old chap as a mentor and he used to use the valves from tv's to make receivers and transmitters, interesting stuff. I must admit that I loved chasing and chatting to distant people. I loved setting up mobile stations for coms purposes, we did one for a flood once it was very rewarding and good fun too................................

[charleville]

Could I go super techy and give you the real explanation of SWR;D


Ah well, then, you would be familiar with Maxwell's equations ...


http://img.skitch.com/20080910-pmr63u5jp9e9jkt8bx5hnahpfq.preview.jpg (http://skitch.com/charleville2/iuqs/untitled)
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;D ;D ;D ;D





Thing is, once I got my kit all working I quickly learned it was all about people trying to contact people as far away as possible, rather than building gear. I lost interest quickly after that.


Ah yes, I remember those old guys with radios built out of the ARRL handbook. They used to discover each other around the world by radio and then send a postcard to the other guy with a photo of their wireless equipment.

I wonder if anyone still does that on the planet today. Seems as pointless as my old 87 year old ex boss (and good mate) who still tries to teach his twenty-ish year old grand-kids about Ohm's law because "it is good to know." ;D

He is the same guy who just loves to construct his own computer by buying all of the components separately and putting them together and then never seeming to ever have it working very well on his dial-up internet service.

Me? I just buy an Apple Macbook, plug it in to my 17 MBit/s broadband service and forget I ever knew of Ohm's Law, Maxwell's equations or bloody SWR, Return Loss and everything that goes with it.


;D ;D ;D


.

.... but wot's all this got to do with fishin'?!!!



;D


.

[QF3 MROCP]

Charlie: tell your old boss to keep trying to teach the 20 yr old...

We are still teaching this in the VHF radio course... P=V*I ... once understood the class students so realize why they get flat batteries

Peter