A little help please

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JPMC
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A little help please

Post by JPMC » Tuesday 4th Jan 2011, 20:02

Hi there,

Just a couple of quick questions and I apologise if this has been asked before. I did a quick search but came up blank.
I'm looking at getting an amplifier for my radio but would like to know a little more about them.
Does a straight amplifier only boost your output signal and to increase both input and output do I need to get an amplifier with preamp?

Also all the amp's I see advertised seem to be rated 1-5watts for AM/FM and 1-10watts for SSB input but I see everybody saying you should turn your radios output to 2watts is this really required if your within the limits for the amp's input?

And lastly are mosfet transistors better than MRF transistors when looking at amp's.

Thanks.

lbcomms
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Re: A little help please

Post by lbcomms » Sunday 9th Jan 2011, 2:50

To avoid disappointment, give a few more details as to what you are trying to do:

Do you mainly use AM or SSB?
Use it for Skip or to talk to the locals?
Base station or mobile?

In short, you need to multiply your power by TEN to double your volume at the other end.
Anything less than that is usually a waste of time.

Taking it further, you need to multiply your power be a HUNDRED (10x 10) to make yourself 4 (2 x 2) times louder.
1200 watts (12 x 100) will need 150+ amps @ 12V, you are going to need bigger batteries, alternators, and wiring in your car.

More info on linears: http://www.radiomods.co.nz/forum/viewto ... f=2&t=2684

If you are just talking to the locals on AM, terrain is a much bigger range limiter than power.

JPMC
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Re: A little help please

Post by JPMC » Tuesday 11th Jan 2011, 13:30

lbcomms wrote:To avoid disappointment, give a few more details as to what you are trying to do:

Do you mainly use AM or SSB? AM
Use it for Skip or to talk to the locals?Locals
Base station or mobile? Mobile
I'm not really up to speed on all the tech stuff but I'll try to understand.

All I'm hoping to achieve is to increase the distance I can send and receive by a few km's, hence I'm looking at only getting a small amp.

lbcomms
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Re: A little help please

Post by lbcomms » Thursday 13th Jan 2011, 23:26

increase the distance I can send and receive by a few km's
Range is a relative thing, not absolute. What is your current range and what do you want yo boost it to?
For example, if you want to increase your range from 10km to 12km then an amplifier will help, but if you want to increase it from 2km to 12km then an amplifier will NOT help you.
The factors that affect your range the most are the terrain between you, and the antennas used on each station.

Can you improve your antenna system? For best performance, you need a 5 to 6 foot antenna mounted near the centre of the vehicle - if you are cutting down of this (like using an AM/FM/CB type, short trunk mount, rubber ducky, etc) then an amp will not give much improvement in range at all.
I'm not really up to speed on all the tech stuff
Hams have known this principle for years - you will get far better improvement spending $100 optimizing your antenna system than spending $300 on an amplifier, and as a bonus, you'll stay legal.

What radio and antenna are you using?

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Re: A little help please

Post by JPMC » Friday 14th Jan 2011, 20:18

lbcomms wrote: What radio and antenna are you using?
I've got a Uniden PRO610XL radio and my current antenna is a centre loaded stainless steel whip 1200mm long (just over 3.1/2ft) but I'm trying to get hold of a Wilson 1000 or maybe a Sirio Hypower 4000 but are struggling as nobody in NZ seems to sell them and although I can buy from either USA or Europe the length causes problems as parcel postage limits are set at 4 foot. I can get long fibreglass antennas locally but I'm not really keen on them and would rather a stainless whip.

As for the range I have at present, normally it's approx 2-3km's. Sometimes when the conditions are right I can get a bit further but I'd like to pump that up to 5 or 6km (Not wanting to jump on top of everyone). My SWR is 1.3 with my current setup.

I also realise that pushing more than 4 watts on CB is illegal which is another reason why I'm not looking to go for huge power or range.

Thanks for replies so far, your a champion :D

lbcomms
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Re: A little help please

Post by lbcomms » Saturday 15th Jan 2011, 14:31

Code: Select all

Uniden PRO610XL 
By that, I'm assuming 510 (couldn't find anything on a "610").
These are a very basic thing, good for convoy use, but not really meant for long range.
centre loaded stainless steel whip 1200mm long
Mounted where and on what type of vehicle?
I can get long fibreglass antennas locally
What do you have against these? The performance (of a properly designed antenna) is determined by its length, not what it is made from.
For 40 channel use, you need an antenna 1M long at least, for 80 to 200 channels, you'll need to go 5 or six feet long.
In all cases, the top 3 feet of the antenna should be above the highest point of anything on the vehicle (except other antennas or nonconductors).
pump that up to 5 or 6km
2.5 times the distance would need 33 times the power, or 130 watts.
I'm not looking to go for huge power
Anything less than 40 watts would be hardly noticeable.

You would be FAR better off optimizing your antenna system (if needed), and buying a better radio.
Have a look for one with SSB (even the cheapest have better filtering than any AM only set) on TradeMe or eBay.

There is a 100 channel SSB on TradeMe currently at $120, have a look here:
http://www.trademe.co.nz/Electronics-ph ... 044220.htm

This would be MUCH more beneficial to tour range than a 100 watt amp.

Cheers

JPMC
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Re: A little help please

Post by JPMC » Saturday 15th Jan 2011, 23:52

lbcomms wrote:

Code: Select all

Uniden PRO610XL 
By that, I'm assuming 510 (couldn't find anything on a "610").
These are a very basic thing, good for convoy use, but not really meant for long range. No it's a 610 the 510's big brother (http://uniden.co.nz/NEW_ZEALAND/p_pro630xl_index.asp#
centre loaded stainless steel whip 1200mm long
Mounted where and on what type of vehicle? Mounted on the passenger side front guard of a Navara ute. Would have it on the centre of the roof but have a cellular aerial there.
I can get long fibreglass antennas locally
What do you have against these? The performance (of a properly designed antenna) is determined by its length, not what it is made from.
For 40 channel use, you need an antenna 1M long at least, for 80 to 200 channels, you'll need to go 5 or six feet long.
In all cases, the top 3 feet of the antenna should be above the highest point of anything on the vehicle (except other antennas or nonconductors).
The only reason I prefer not to have fibreglass is I go into a lot of places with low trees and bushes (not to mention car park buildings too) and from past experences the fibreglass antennas don't take the beatings to well but the stainless whips do. With my antenna about 2 thirds of it is above the roof line (pretty much from the centre loaded piece up) but as already stated I'm wanting to upgrade it and would definitely have too if getting an amp as manufacture of current one states it's only rated to 30 watts.

lbcomms
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Re: A little help please

Post by lbcomms » Sunday 16th Jan 2011, 2:43

No it's a 610 the 510's big brother
That's a 630, not a 610 - that explains why I couldn't find it :o :)

In any case, the stuff that matters (good filtering and good noise reduction, amongst other things) is the same as the 510.
They are a nice looking thing, nice to use thing with the scanning etc, but as a radio - rather mediocre...
Useful for convoy work where looks are important, like the Toyota landcruisers (that have never seen a dirt road) we see here every weekday morning, dropping kids off at the local mega$ catholic schools. Not so good where decent performance is needed.
Mounted on the passenger side front guard of a Navara ute
That will get out well to anyone in the direction of the right-hand side rear, not so good in other directions.
It's also going to pick up more noise from the EFI, charging, and ignition systems.

Is there a bar behind the cab? If so, mount it there.
Image

Mounting a good antenna there and getting a radio with decent RF performance will give you much better results than a 100 watt amplifier...

JPMC
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Re: A little help please

Post by JPMC » Sunday 16th Jan 2011, 21:40

lbcomms wrote:
Mounted on the passenger side front guard of a Navara ute
That will get out well to anyone in the direction of the right-hand side rear, not so good in other directions.
It's also going to pick up more noise from the EFI, charging, and ignition systems.
Yeah your spot on with the direction but I can run the squelch turned right down and get bugger all interference from the vehicle at all. The only interference I seem to get is from overhead powerlines every now and again and only in certain weather conditions (Really irates me)

Is there a bar behind the cab? If so, mount it there. No sorry just a canopy but could posibly put a angle bracket off the back of the cab or would a dual antenna setup on the guards work if antennas where longer?


Mounting a good antenna there and getting a radio with decent RF performance will give you much better results than a 100 watt amplifier...
Been looking around and it appears that all the long fibreglass antenna's have disappaired from the NZ market and the longest I can find available is either the one I have or a 1.5m GME hi performance antenna (fibreglass).
What do you think of this radio? http://www.trademe.co.nz/Electronics-ph ... 613498.htm

I spend most of my time on channel 11 but sometimes just leave it scanning all channels and pick up the ham guys talking on channel 26 so next time I hear them I might break in and ask them of places I could get a good antenna locally.

lbcomms
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Re: A little help please

Post by lbcomms » Tuesday 18th Jan 2011, 1:27

could posibly put a angle bracket off the back of the cab
That would be close to ideal, just make sure the bracket is directly grounded (i.e. don't use an earth wire, the bracket must join directly to the metal car bodywork)
would a dual antenna setup on the guards work
No. Your radio puts out X watts (4 in your case) and therefore (following the law of physics that states that energy cannot be created) the signal radiated by 2 antennas CANNOT be any stronger than a single antenna. Some big trucks use duals, but that's for a different reason altogether.
1.5m GME hi performance antenna (fibreglass)
That would be ideal performance wise, but you'll have to remember to take it off when you go into underground carparks and the like.
but sometimes just leave it scanning all channels
The trend for radios is for features like scanning, backlighting, beeps, and fancy LCD displays - the reasons are it looks nicer (easier initial sale to noobs) and low cost (micro code costs nothing once it's developed, for example). These new "features" do NOTHING for the RF performance, like good filtering that costs real $ does.

In 1.5 sentences: get your antenna system in order, then buy a decent (SSB equipped) radio if you are still not happy with your transmission range. If you are still not happy once you have done the antenna and radio, THEN look at amplifiers.

Cheers

JPMC
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Re: A little help please

Post by JPMC » Tuesday 18th Jan 2011, 14:58

Cool.

Thanks very much for the help. :occasion5:

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