Re: Very Interesting Radio - Possible Sat Use (maybe not)
I purchased an interesting radio that might be an inexpensive way to operate full duplex on the FM sats. The radio cost $65 including shipping and all accessories. It runs 2W on both 2M and 70cm. It has almost all the bells and whistles you would expect on a dual band handi. 99 memories - tone squelch ... http://www.tomdoyle.org/UV-X4.jpg
There have been various postings and publications in QST and Funkamateur about the brother of this radio, the Baofeng UV-3R, and it's very poor harmonics filtering on the 2m band. Harmonic suppression was something like 15-20dB. I recently measured an UV-3R mark 1 (single frequency on display) and confirmed that the very poor filtering was indeed the case.
Since these things transmit from 136 - 174 I tuned frequency a bit and found that suppression is OK at 165 MHz and above, and gets worse as the frequency goes down. On 136 MHz (on which I don't transmit except on a dummyload of course), I found that harmonic suppression was *negative* in some cases. Some of the publications confirm this, so my measurements are sound and it's not an incidental case.
On request of the owner, I did the "capacitor mod" (adding a capacitor to the lowpass filter) and found that the suppression was still inacceptable.
I purchased an UV-3R mark 2 (dual frequency on display) and established that while it was "mark 2", the harmonic suppression was as poor as a Mark 1 radio. I have not voided the warranty yet on this radio to do the capacitor mod on the Mark2 radio, but I'm not hopeful.
While some people claim that "it may pass the specs because the Mk1 radio comes with separate antennas for VHF and UHF", the mark2 comes with a dualband antenna and for sat work, with an Arrow antenna or similar, harmonic attenuation of the antenna is nonexistant - we sat hams use good antennas!
Mail sent to the manufacturer address in the manual on this issue remains unanswered.
The Dutch regs specify '-36 dBm or -60 dBc, whichever is highest' and this radio doesn't even come close. FCC regs may be less tight, but I think our transmissions should be to the highest standards and frankly, this radio doesn't come close.
My conclusion so far is that the thing may be good enough for listening, but when you want to transmit then this radio is only useful if your table tips and you need something to remedy that, but not for making QSO's.
I have not measured the UV-X4 but have been told the internals are the same - the controls are in the same position, in any case.
73,
Geert Jan PE1HZG
PS: the separate charger does not have any protection circuitry in it and depends on the protection circuitry in the battary itself to charge (and protect) a dangerous LiIon cell. Personally I would not use this unless I have it in sight and a way to remove power quickly - these cells are temperamentful when overcharged, and the battary protection circuit is not intended to replace a correctly designed charger protection circuit..
You get what you pay for.2 watts on a satellite would be tough to use and be heard anyway with all the big guns out there. But it still maybe good enough to use .Full duplex is not necessary if one knows how to use a HT. I have used the wouxoun 144/440 on the birds with great results. WA4HFN
----- Original Message ----- From: "Geert Jan de Groot" [email protected] To: [email protected] Sent: Friday, January 13, 2012 5:00:24 AM Subject: [amsat-bb] Re: Very Interesting Radio - Possible Sat Use (maybe not)
I purchased an interesting radio that might be an inexpensive way to operate full duplex on the FM sats. The radio cost $65 including shipping and all accessories. It runs 2W on both 2M and 70cm. It has almost all the bells and whistles you would expect on a dual band handi. 99 memories - tone squelch ... http://www.tomdoyle.org/UV-X4.jpg
There have been various postings and publications in QST and Funkamateur about the brother of this radio, the Baofeng UV-3R, and it's very poor harmonics filtering on the 2m band. Harmonic suppression was something like 15-20dB. I recently measured an UV-3R mark 1 (single frequency on display) and confirmed that the very poor filtering was indeed the case.
Since these things transmit from 136 - 174 I tuned frequency a bit and found that suppression is OK at 165 MHz and above, and gets worse as the frequency goes down. On 136 MHz (on which I don't transmit except on a dummyload of course), I found that harmonic suppression was *negative* in some cases. Some of the publications confirm this, so my measurements are sound and it's not an incidental case.
On request of the owner, I did the "capacitor mod" (adding a capacitor to the lowpass filter) and found that the suppression was still inacceptable.
I purchased an UV-3R mark 2 (dual frequency on display) and established that while it was "mark 2", the harmonic suppression was as poor as a Mark 1 radio. I have not voided the warranty yet on this radio to do the capacitor mod on the Mark2 radio, but I'm not hopeful.
While some people claim that "it may pass the specs because the Mk1 radio comes with separate antennas for VHF and UHF", the mark2 comes with a dualband antenna and for sat work, with an Arrow antenna or similar, harmonic attenuation of the antenna is nonexistant - we sat hams use good antennas!
Mail sent to the manufacturer address in the manual on this issue remains unanswered.
The Dutch regs specify '-36 dBm or -60 dBc, whichever is highest' and this radio doesn't even come close. FCC regs may be less tight, but I think our transmissions should be to the highest standards and frankly, this radio doesn't come close.
My conclusion so far is that the thing may be good enough for listening, but when you want to transmit then this radio is only useful if your table tips and you need something to remedy that, but not for making QSO's.
I have not measured the UV-X4 but have been told the internals are the same - the controls are in the same position, in any case.
73,
Geert Jan PE1HZG
PS: the separate charger does not have any protection circuitry in it and depends on the protection circuitry in the battary itself to charge (and protect) a dangerous LiIon cell. Personally I would not use this unless I have it in sight and a way to remove power quickly - these cells are temperamentful when overcharged, and the battary protection circuit is not intended to replace a correctly designed charger protection circuit..
_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (2)
-
Geert Jan de Groot -
wa4hfn＠comcast.net