Walkie Talkie Kakie (FRS & GMRS)

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FrancisTLim
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby FrancisTLim » Sat Dec 12, 2009 11:30 am

charade wrote:Another thing i need to know is..if i set the frequency more big i.e 490 MHz..
can or cannot the walkie talkie range go over 5KM or something....
No. The range is not directly related to the frequency. It depends on the design of the aerial, and also the surroundings. There is no clear-cut winner whether high or low frequency is better, because they have their own characteristics (eg. wall penetration, reflection from objects, length of aerial, etc.) The best method is to test using your actual situation (eg. car to car, then you must actually sit in two cars) and test the different frequencies and different sets. You will be quite surprised that changing the power (1W, 2W, etc.) has not much effect on the range, unless the power difference is really great (eg. 1W and 5W). This is because of the Inverse Square Law. So you actually have to increase the power 4 times just to get a doubling of distance.
Last edited by FrancisTLim on Sat Dec 12, 2009 11:40 am, edited 4 times in total.
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FrancisTLim.

FrancisTLim
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby FrancisTLim » Sat Dec 12, 2009 11:35 am

chaicka wrote:
tks wrote:
stratman2 wrote:10 miles range, are you sure? :ko: Or did you mean 10 kms instead?


US sets show the range in miles and 10 mile sets are very common. My Motorola T6500 claims 10 mile range. My Motorola T9510 claims a ridiculous 40 km range !!!


On paper specs that is.

T6500 - 10 mile set, most likely end up around 2-3km range on NSW, if use on B roads, range shortens even more.

Dun trust the paper specs, look for output power specs instead. And if the sets have relay-capability, then it will improve overall convoy's comms, depending on how far the 1st and last vehicle stretch, type of roads, weather, and how many sets within the convoy has relay-capability.

Haha!! You are absolutely right. Just ignore the written distance (range)!! When it started a few years ago, Motorola tried to be conservative and put a reasonable range (eg. 2 miles). Then the other brands started to claim very long ranges (20 miles) so Motorola had no choice but to keep up.

Anyway, power is important, but what is more important is the length of the aerial (generally speaking). I have seen some GMRS models which are supposed to be 5W, but they have very short aerials. There are some Motorola sets which are only 2W, but they have very long aerials. They perform so much better.
Regards,
FrancisTLim.

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tks
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby tks » Sat Dec 12, 2009 11:47 am

Hi I am well aware that the claimed range on the box is very misleading. I have also tried those higher W sets but there are just the same. When Motorola was selling only max 5 miles sets with I think max 1W output, I tried those Midlands sets with claimed 2 to 3W output. Midlands claimed that with much higher output, their range is much further. I tried them. No difference. In fact, I think their performance was even worse. And the build quality, very plasticky, was just not there. I sold them and went back to Motorola.

I am still looking for a suitable set. Any recommendations? It must be one of those sets that are approved for licence free use in the US/Canada or at least barely legal there. It should at least look like the Motorola FRS radios coz I don't want to be seen carrying obviously commercial radios without licence.

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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby yoladu » Sat Dec 12, 2009 12:09 pm

FrancisTLim wrote:Anyway, power is important, but what is more important is the length of the aerial (generally speaking). I have seen some GMRS models which are supposed to be 5W, but they have very short aerials. There are some Motorola sets which are only 2W, but they have very long aerials. They perform so much better.


Power is important solely for better transmission.

Antenna length per se is not important but what is critical is that the antenna length must match the frequency wave length.

For FRS, PMR446, all in the UHF band, the length of antenna offers little advantage as the designated frequency spectrum is very narrow.

For VHF antenna, there is a table so that the antenna can be cut to match the frequency of the radio.

:)
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yoladu
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby yoladu » Sat Dec 12, 2009 12:34 pm

tks wrote:I am still looking for a suitable set. Any recommendations? It must be one of those sets that are approved for licence free use in the US/Canada or at least barely legal there. It should at least look like the Motorola FRS radios coz I don't want to be seen carrying obviously commercial radios without licence.


Your best bets are those Motorola FRS/GMRS radios, but all these radios always look like toys. The power output is limited by the FCC requirements so you will never get good range.

UHF range is line of sight, so technically both users on standing on flat ground, 10km is about the max but transmission is poor due to low power output. As a result, effective range is usually less than 5km.

if you want a UHF radio that has good range, get an Icom radio, they have an output of 4w but they have a professional outlook.

:)
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chaicka
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby chaicka » Sat Dec 12, 2009 7:01 pm

FrancisTLim wrote:Haha!! You are absolutely right. Just ignore the written distance (range)!! When it started a few years ago, Motorola tried to be conservative and put a reasonable range (eg. 2 miles). Then the other brands started to claim very long ranges (20 miles) so Motorola had no choice but to keep up.

Anyway, power is important, but what is more important is the length of the aerial (generally speaking). I have seen some GMRS models which are supposed to be 5W, but they have very short aerials. There are some Motorola sets which are only 2W, but they have very long aerials. They perform so much better.


I think somehow you are right. I had an older Motorola model which states 8 miles (parallel imported almost 7-8 years back), and compared to the set used in recent road trip (provided by the road trip organizers, has a paper specs range of 20km), my almost decade-old set (place in cup holder near gear stick) was able to pick up the conversation when the provided set (VC holding) was breaking up badly.

Oh... the provided set has longer antenna too... Is that the length of aerial you mentioned?

chaicka
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby chaicka » Sat Dec 12, 2009 7:03 pm

yoladu wrote:
tks wrote:I am still looking for a suitable set. Any recommendations? It must be one of those sets that are approved for licence free use in the US/Canada or at least barely legal there. It should at least look like the Motorola FRS radios coz I don't want to be seen carrying obviously commercial radios without licence.


Your best bets are those Motorola FRS/GMRS radios, but all these radios always look like toys. The power output is limited by the FCC requirements so you will never get good range.

UHF range is line of sight, so technically both users on standing on flat ground, 10km is about the max but transmission is poor due to low power output. As a result, effective range is usually less than 5km.

if you want a UHF radio that has good range, get an Icom radio, they have an output of 4w but they have a professional outlook.

:)


How's the Motorola MR series (eg. MR350R)? I am looking at getting replacement sets to replace my almost decade old 8-miles set, and it has to be compatible with most common motorola sets coz often used by pple in road trips that I join.

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dvpro
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby dvpro » Sat Dec 12, 2009 7:28 pm

chaicka wrote:...
I am looking at getting replacement sets to replace my almost decade old 8-miles set, and it has to be compatible with most common motorola sets coz often used by pple in road trips that I join.

If you don't mind using illegal set :-' , a 4 Watt- Puxing PX-888 or Puxing PX-777 may fit the bill. Frequency can be input using keypad and with frequency range between 400~470MHz (UHF model), it should cover US FRS channels (maybe minus CTCSS tones). If I remember correctly, a friend of mine bought his PX-888 for about RM500/pc. A feature I find interesting with PX-888 is the dual channel watch, ie. main channel can be set for group communication, while the secondary channel for private communication with your partner.
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FrancisTLim
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby FrancisTLim » Sun Dec 13, 2009 9:00 am

yoladu wrote:Antenna length per se is not important but what is critical is that the antenna length must match the frequency wave length.

Ahh... Just to avoid misunderstanding, I am referring to the external visible stub length of the aerial on the set. Most (I hope) manufacturers try to have the actual wire length of the aerial to "match" (ie. electrically match) the frequency, but after that, they coil the length of the aerial wire into a short stub. This is to save space. Wire length is about 16cm for quarter-wave aerial at GMRS/FRS frequencies. Most GMRS/FRS sets I have seen have stubby aerials of lengths between 3cm to 7cm. If you cut open the rubber/plastic shell of the aerial of a GMRS/FRS set, you will see what I mean.

It is the external visible length of this rubber coated aerial of the GMRS/FRS set that I am referring to because that is what you can see when you buy the set. Generally speaking, the longer this aerial is, the better the range. I tested quite a number of sets when I was in the USA, and this proves to be true. Even the lower power sets with longer looking aerials give better range than the supposedly higher power sets with shorter looking aerials.
Regards,
FrancisTLim.

charade
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Re: Walkie Talkie Kakie (FRS & GMRS)

Postby charade » Mon Dec 14, 2009 11:04 am

Thanks all Sifu2 for the xplainnation...

:tq:

NewBie
:)


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