I’ve just tried my new DTRs (x1 650 x2 410) and it seems like the range is lacking somewhat. I remember someone on RadioReference saying that they got very good distance on theirs, while mine seem to be limited to 200 ft or so. Any recommendations on usage, or possibly solutions? I’m going to update their versions once I get a flash cable, so maybe that could be the problem?
EDIT:
I changed out the antenna on my 650 with the one I have on my VHF/UHF one and the extra length seems to have done some good. This solves the problem with the 650 but not the 410’s.
I have a bunch of 550’s with the medium-length antennas and the range on these is much better indoors than any other Radio I’ve seen, including Professional 4 watt Motorola UHF radios.
Do the 410s just have the stubby antennas? I haven’t checked the range on the stubbies.
I don’t know that the firmware update will change anything, but then again, I never tested mine for distance before I updated them.
The 410’s do have stubby antennas. I’m thinking that antenna length may be my issue. As you said indoors, they work amazingly. However take them outside and you lose distance pretty quickly. Now granted all this is at my home, and I haven’t had the chance to do any tests in the area where they would likely be working (Where the LOS is completely different).
I think the higher frequency of the radios (900mhz) makes them more suitable indoors, and the lower frequency UHF radios (~450mhz) and even lower VHF (~150mhz) are better for outdoor use.
My needs are for indoor use so the higher frequency of the DTRs makes them perfect. I would think though, that with the longer antennas, like the full-length ones they sell (but you cannot put on the 410) would give you a better range outdoors.
Hello all,
Beware of changing aerials… the length doesn’t necessarily have anything to do with the gain. The stubbies might well be more efficient than the longer dipoles. Aerials are tuned to the frequency… you have probably noticed that lower frequency radio-microphones have longer aerials , so make sure you fit the correct ones.
The lower the frequency the longer the wavelength and the greater the range. Longer wavelengths pass through mountains while short ones will not pass through your body! The BBC World service is received thousands of kilometres away… wavlenth 198 Meters. Satellite signals are stopped dead by the leaves on your trees… wavelength sometimes less than a centimetre (40GHz).
But at higher frequencies more bandwidth is available, and so more channels, and the signals bounce off the walls, creating a sort of natural “diversity”.
With the old analogue desks (even Midas! etc.) we used to put one hand around the “stubbie” of our Motorolas when transmitting so as to avoid breakthrough into the audio circuits. One hand was enough to greatly reduce the power emission.
David.
There are 3 sizes of antenna for the DTR radios and they are all correct for those radios (only the medium and long ones are replaceable, the stubby ones are not removable).
The longer ones do boast a greater distance and they have been tested and verified to do so.
I’ve verified 3 miles between two DTR550s with the half-wave (longest) antennas, in a suburban setting with the typical trees and houses. Buildings with substantial amounts of metal construction or hills getting in the way will reduce that considerably.
Sorry to butt (intentional) in again but…
Beware of changing aerials… the length doesn’t necessarily have anything to do with the gain. The stubbies might well be more efficient than the longer dipoles. Aerials are tuned to the frequency… you have probably noticed that lower frequency radio-microphones have longer aerials , so make sure you fit the correct ones.
Google about if you want to understand aerials. The development during the cold war was phenomenal. But basically, the lower the frequency the greater the range… and then it is all about power (and precise tuning) (and direction)… so if you have the power it will go further, if your frequency is lower it will go further, and if your tuner is better then it can “home in” on a weaker signal. If you know where your “client” is then you can use a “yagi” for a fixed link… if not it is ALL about power …etc etc.etc…
You are probably all sound engineers…
Its the same thing… a horn (directional) sends it further!
A line array (cohesive wave front - very unidirectional) goes EVEN further (but if you are deaf ((low sensitivity-bad tuner-bad firmware?)) you will not hear it)!
If you pile up your PA the vertical spread is reduced (sort of the “pre” line array) and the sound goes further (horizontally) much like a “stubbie”.
The bass (yes! lower frequency) is heard better further away! It “travels”.
If you put your head in a bass bin 4 miles away then you can hear the pacific ocean (sort of)!!! (it is a tuned circuit- put your head in a Ping-Pong ball and the experience will be “different”)!
BUT… if you feed the bass into the tweeter (wrong aerial) you will not get much out… simple… I hope?
David.
You’re partially correct, in that the length doesn’t necessarily have anything to do with the gain, if you’re just using various lengths of wire without attention to the resonant frequency. However, I think that in this case we’re discussing three antenna types that were designed for resonance on the 902-928 MHz ISM band that the DTRs use.
Typically, a quarter-wavelength antenna is the shortest that will resonate without “loading”, which uses inductance and/or capacitance to make a short wire appear electrically longer at the cost of reducing the radiated power. A quarter-wave antenna at 915 MHz would be just over three inches long, so the “stubby” DTR antenna is clearly a loaded one, and will not be the most efficient radiator.
( A simple but useful formula: quarter-wave length in feet = 234 / frequency in MHz )
I’ve heard, though I haven’t confirmed by dissection, that the medium and long DTR antennas are quarter-wave and half-wave, respectively, and that would appear to be fairly close to their actual lengths. In such a case, where we know both antennas to be designed for resonance, you would expect to see higher transmit gain from the half-wave antenna in any direction perpendicular to its length. That gain will help on receive, too, as will simply having more wire sticking out.
Just to add, I’ve compared the DTR650 range with HT1250 and HT1550 radios(both UHF) and the range of the DTR’s were just as good and what really is a positive is the longer battery life than the HT series.
I actually was looking at the XPR7550 series radios, since they are digital, but in UHF… and curious how well they’d compare to these. Doubt anyone would have compared these though.
A few years back, a friend and I tried a DTR650 test in the California desert. My friend was in Shoshone CA, while I was in Tecopa CA, nine miles away as the crow flies. We were both at our respective ground levels, with an elevation change of just over 27 feet per mile between the two towns. Communications were solid with the DTR radios, which had their stock 7" whip antennas. Both of us are hams, so we tried, as a comparison, communicating with 2 meter FM handhelds, mine using a 5/8-wave telescoping whip. With squelches wide open, we heard absolutely nothing when the other person transmitted. Even when transmitting five watts on 2 meters, there was no hint of a signal present at the receiving site- just white noise. The DTR radios, which worked great, transmit just one watt. That test was a real eye-opener. I wish that we had had more time to experiment because, based on how solid the DTR communications were at nine miles, the range might well have been even farther.