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Old 28-10-2012, 17:21   #31
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Re: Shroud as SSB Antenna?

Quote:
Originally Posted by Dockhead View Post
I have a license good for both VHF and SSB - as a US citizen I'm entitled to a no-exam operator's license. I think about a ham license but wonder whether it's worth the trouble.
...
Depends upon your intended use. Two reasons you might consider it:

1. Nets. There are a lot of nets out there that don't run on standard ITU SSB channels.

2. Services. Some email services, like WinLink, require you to have a HAM license.

Getting a Technician class license is not hard. Provided that you live near an exam location.
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Old 29-10-2012, 11:42   #32
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Re: Shroud as SSB Antenna?

Dockhead,
Drifting ever so slightly.....


1) If you desired a ham license, as a US citizen, you'd get a FCC issued US ham license.....(I always assumed you were a UK citizen....sorry about that...)
And, if you've got a US-flagged vessel, you could use an Icom M-802....for both maritime and ham operations.....







2) However, with your earlier statements in mind, aside from picking up some technical knowledge along the way, I'm not sure that ham radio is something that you'd get much from...
Quote:
Originally Posted by Dockhead View Post
I think about a ham license but wonder whether it's worth the trouble.
Quote:
Originally Posted by Dockhead View Post
Well, I would want a real marine SSB radio in any case, so a ham license wouldn't help me there. Seems a lot of trouble just for Winlink (Winlid?) when Sailmail is available, and you are allowed to use Sailmail for business purposes. Are there nets on ham frequencies which are not accessible to marine SSB operators? What is there to do besides logging long distance contacts?
...Yes, there are MANY MANY ham frequencies (and Nets) that are not accessible to anyone other than licensed ham operators....but, unless you are "into" radio communications, propagation, & electronics, and desiring to improve knowledge & skills in these areas / communicating with others over radio, and continuing the advancement the radio art / participate in public service and emergency communications / promote international goodwill via ham radio / etc.... then perhaps ham radio is not for you???


The establishment of the amateur radio service (ham radio) worldwide was done (and continues to flourish) because of very specific reasons, and very specific international rules/purpose were set down many years ago, by international agreements....


For US citizens (or others who qualify for a US amateur radio license), these purposes/rule are very specific, and should be understood by all who desire a "ham radio license"....(and should be remembered by all of us who already have licenses!!!!)
Here they are:
Quote:
97.1 Basis and purpose.-

The rules and regulations in this Part are designed to provide an amateur
radio service having a fundamental purpose as expressed in the following
principles:

(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.

(b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communications and technical phases of the art.

(d) Expansion of the existing reservoir within the amateur radio service of
trained operators, technicians, and electronics experts.

(e) Continuation and extension of the amateur's unique ability to enhance
international goodwill.






Please understand that while there are many (like myself) that think that sailing and ham radio go well together....the fact is that ham radio just isn't for everyone!!!
And, not being interested in it, is perfectly fine!!!!


So, if you feel that maritime comms (voice and data) would be sufficient for you, you are probably correct!!!
But, should any of the above 5 main purposes/principles of amateur radio appeal to you, then have a look at www.arrl.org and proceed to get your license and enjoy!!!





Fair winds...


John
s/v Annie Laurie
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Old 29-10-2012, 11:57   #33
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Re: Shroud as SSB Antenna?

There are a few points: is it a receiving antenna or both, receiving AND transmitting.

That makes a big difference.

You can make your own antenna if you are able to spend a little time, saving you a lot of money.
If you need reception of VHF,UHF,AM,FM,SW - there are very simple solutions costing little.

Google on SSB antenna and a new world will open.

To use a shroud or stay is a very bad idea. Stainless steel is a poor transmitter.

I have figured it out now for my own multiband reveiver, having in production my own antenna.
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Old 30-10-2012, 02:50   #34
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Re: Shroud as SSB Antenna?

McG,


if using a backstay as an antenna were a bad idea than unfortunately thousands and thousands of sailing yacht have a very bad antenna system installed by completely inadequate technicians....

The little extra Ohmic resistance adding to the radiation resistance of the SS wire means litlle. Not to worry at all.

If you can make an alternate "backstay" wire antenna made from strong copper wire, the better but you can use SS lifeline cable or the tinned steel wire used a lot for wire HAM antennas (the latter can be soldered!).

Even if some will contradict me I do think for the short ( shorter than 1/4 wave of any target frequency) ground lead connection between the antenna tuner and a single unbonded underwater bronze or bronze plate you should preferanbly use wide copper tape/foil (protected against corrosion) and not copper wire or tinned copper braid.

If using ground radials or bonding any other metals on the boat (lifelines, pulpit, toerails, metal tanks) they will be SS or aluminum so no choice and they will also work.

Jan
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Old 30-10-2012, 03:01   #35
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Re: Shroud as SSB Antenna?

OK, just one more question: My backstay is 24 meters long. Where should the insulator go? Should I avoid certain lengths because of resonance on particular frequencies, or how is it done?

Is it too much metal? It's 16mm thick, so it weighs about 24kg.
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Old 30-10-2012, 03:27   #36
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Re: Shroud as SSB Antenna?

This is the way as adviced to me. I spent much time to check what was for me the best solution.
If an antena specialist claims that stainless has a lot of noise as a sideffect, I tend to be a believer. These people are specialists.

In any case, nobody tells you what to do so follow your own idea' s as I do mine.

I do not need to transmit, I have just a receiver. And I am not cutting into my rig.
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Old 30-10-2012, 03:41   #37
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Re: Shroud as SSB Antenna?

Hi Dockhead;

several answers:

1. No your backstay isn't too thick, the high frequency current "moves" on the outer surface (skin effect) and stainless is no issue

2. No it is not too thick, a thick "fat" antenna is even an advantage since it improves bandwith and lowers the impedance (alternate current resistance...) of end-fed wire antennas, although at the typical HF frequencies that effect will be minimal (you would need to have an antenna that is 15cm "thick" to really start profiting from that). So: NO it is not a disadvantage having 16mm thick cable.

3. Lengths to avoid: be careful here:
=> we are always talking about TOTAL ANTENNA LENGTH meaning: from the top of your wire/cable (at the top isolator) UNTIL the antenna lug on the antenna tuner.
=> So you have to count in the wire that will lead down from the top of the lower insulator (in case of isolated backstay antenna) or the chainplate of the backstay (in case it is fixed in an isolated way in the GRP of the hull as it usually is). Bear in mind: if you have a backstay tensioner hydralulic or even mechanic in my eyes it is a BAD idea not to have a lower isolater and feed at the chainplate.
=> decide on WHICH FREQUENCIES you will want to work: HAM - which? Marine SSB - Which?

=> you have to avoid a (total) antenna length that is close to 1/2 Wave multiples for any target frequency.
The formula is easy: Divide 150 by the frequency in Mhz - this gives the theoretical half-wave length to be multiplied by a"velocity factor" for a mainly SS cable that will certainly be around 0.95 or somewhat lower.

An example:
Marine SSB net on 12.359 Mhz
150/12.359*0.95 = 11.53 metres.

Avoid a total wire length (untill ATU) of around 11.5m. (or your tuner might be unable to tune this frequency)

10.5m and 12.5m should do.

The typical 40 ft of isolated backstay (12.2m) with 1,5 m of GTO-15 wire leading to the ATU antenna lug give a total of 13.7m antenna length.

Now let's do the opposite excercise: 13.7m wire /0.95 gives 14.4 metres "electrical" wire length (trust me...).
150/14.4 gives: 10.44 Mhz - this means this antenna length is about a halfwave for 10.44 Mhz and hence quite close to the HAM 30m band, that might be difficult/impossible to tune (nor harm it is mainly morse and digital modes no voico communications).

Make yourself a little spreadsheet with your target frequency bands and applying the formula. Add also 300/frequency and 450/frequency for 2/2 wavelength and 3/2 wavelength and you will have a fine table showing you total antenna lengths to avoid.


Sorry for the theory....

Jan
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Old 30-10-2012, 04:21   #38
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Re: Shroud as SSB Antenna?

Ver well McG.
Money has to roll to make the economy turn!

If you wish to spend like $400 or more on 2 bunches of parallel wire (really very heavily overpriced...) and this only to receive.....

By all means do so! The seller will be happy!

Seriously now, for a receiver this is really an overkill and this GAM antenna is designed to be used with an antenna tuner.
You will be 50 times cheaper hanging a marine-grade tinned isolated copper wire from a spare halyard and use that as an antenna.
If you want a little bit of sofisitication, bring it down to deck level and hook it on a 1:4 weatherproof UNUN, from there 50 Ohm coax to your receiver, and while you are at it, connect some form of ground to the Unun's ground lug...to deal a bit with "noise".

If you want to optimise and tune at receive, there are some small compact SWL antenna tuners (MFG) - you just tune on highest receiving signal strength.

In that way you also "roll the bucks" but you will have a far better SWL system than an expensive GAM and a receiver......

Sorry to be bold....
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Old 30-10-2012, 05:05   #39
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Re: Shroud as SSB Antenna?

Sorry for the off-topic drift...

MacG,
sorry I said MFG but off course it is MFJ tuners.

This is the link to a cheap random wire tuner:

http://www.mfjenterprises.com/Produc...ctid=MFJ-16010

At $ 69.9 not that expensive and compact.

Tune you wire antenna on highest RX signal strength on your receiver...no need for a transmitter and SWR meter.

Of course you need to bring down the wire antenna into the NAV station or any dry area where you want to put this manual tuner. From the tuner a coax to your receiver.
Do connect some form of grounding to the ground lug on this tuner (a short wire to SS fuel tank, or to lifelines and stanchions, or an underwater bronze) it will improve your RX system.

Jan
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Old 30-10-2012, 05:22   #40
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Re: Shroud as SSB Antenna?

@ Jan

I made them myself in line of what you posted before. Not this $ 400 piece.

I have used insulated tinned braided loudspeaker wire of approx 4mm thickness with a home made 4:1 balun. According to specs of an antenna specialist.

I have a 4 band receiver made by STE, not the most recent technique but very stable and did come from a small class warship.
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Old 30-10-2012, 05:35   #41
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Re: Shroud as SSB Antenna?

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Sorry for the theory....

Jan
Sorry for the theory?? On the contrary, thanks very much!!

What frequencies are the most useful on SSB and for what purposes? Then I'll be able to apply your table and see what lengths to avoid.

Thanks!
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Old 30-10-2012, 05:55   #42
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Re: Shroud as SSB Antenna?

Go the gam works great and a one armed monkey can do the install in an hour well made no need to cut anything plug and play dont know who the australian distributor is tho
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Old 30-10-2012, 05:57   #43
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Re: Shroud as SSB Antenna?

I would say so. It is always good to discuss such items. One can only learn.

I have a number of fixed settings (430-440 MHz) and a large, very fine tunable dial with antenna tuner.
It is a 7-10 m receiver
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Old 30-10-2012, 06:16   #44
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Antenna tuner, balun, or unun will add very little to receive only activities. I would avoid the complication. And for receive only, longer is almost always better in an antenna.

For antenna length for transmitting, one has to decide on use. Sailmail and marine SSB bands or Winlink on ham bands? Chat only on ham bands?

For Winlink you will use mostly the 20, 30, 40, and 80 meter bands (14.1, 10.1, 7.1, and 3.6 mHz). For Sailmail and marine SSB 2, 4, 8, 12, and 16 mHz (look them up, I don't use them).

You can do the calculations for lengths to avoid.

And staiinless steel antennas are not "noisier" than copper. Whoever says that is not an expert.

Chip
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Old 30-10-2012, 06:21   #45
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Re: Shroud as SSB Antenna?

Quote:
Originally Posted by Goudurix View Post
Ver well McG.
Money has to roll to make the economy turn!

If you wish to spend like $400 or more on 2 bunches of parallel wire (really very heavily overpriced...) and this only to receive.....

By all means do so! The seller will be happy!

Seriously now, for a receiver this is really an overkill and this GAM antenna is designed to be used with an antenna tuner.
You will be 50 times cheaper hanging a marine-grade tinned isolated copper wire from a spare halyard and use that as an antenna.
If you want a little bit of sofisitication, bring it down to deck level and hook it on a 1:4 weatherproof UNUN, from there 50 Ohm coax to your receiver, and while you are at it, connect some form of ground to the Unun's ground lug...to deal a bit with "noise".

If you want to optimise and tune at receive, there are some small compact SWL antenna tuners (MFG) - you just tune on highest receiving signal strength.

In that way you also "roll the bucks" but you will have a far better SWL system than an expensive GAM and a receiver......

Sorry to be bold....

jan -- i have heard this many times before -- so please let me ask one question - given your description why is almost everyone put in a backstay antenna with either the gam electroics antenna or insulators??
Are you so correct and everyone else so wrong are what? sorry to be so bold but i guess most cruisers out here are wrong and you are right?????

just my thoughts and opinions
chuck patty and svsoulmates
in trinidad for hurricane season
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