[amsat-bb] Re: more about the TH-D72A for satellites
kq6ea at verizon.net
Sun Dec 5 21:37:28 PST 2010
I've been considering "retiring" my TH-D7, and I think you just sold me
on the new Kenwood!
73, Jim KQ6EA
On 12/06/2010 04:24 AM, Patrick STODDARD (WD9EWK/VA7EWK) wrote:
> I wavered on whether I was going to get this radio straight away, after
> the fiasco (related to FM satellite operation) the Alinco DJ-G7T was
> last year. I didn't want to get bitten by a radio that was supposed to
> be capable of full-duplex operation, but fall short like with the DJ-G7T.
> After some thought, and after yesterday's hamfest, I drove over to the
> local HRO store to see if they had any in stock. At mid-afternoon, HRO
> still had 3 on the shelf at this store. I decided that, if the TH-D72 is
> the true successor to the TH-D7 including the cross-band full-duplex
> capability for FM voice satellite operation, I'd take the plunge. I
> bought the radio and the only option they had for it in the store
> (cigarette-lighter cable, compatible with several other Kenwood HTs
> including the TH-F6A I purchased a few weeks ago).
> I charged the battery last night, and cleared some time this afternoon to
> go out to my favorite city park to try it out. Not having used a Kenwood
> HT on the satellites except for the TH-F6A as a receiver, I read through
> the manual to make sure I had it set up for FM satellite work. I looked
> at a few parameters I felt would be useful:
> 1. Transmit with VFO B, receive with VFO A. VFO A has better sensitivity
> than VFO B, so why not go with that? There is no restriction on which VFO
> can be the transmitter for this radio.
> 2. Audio balance. I set that all the way to VFO A, since I wasn't
> interested in hearing VFO B. I could see with the S-meter if anyone else
> was transmitting on the satellite uplink, and then rebalance the audio if
> necessary to hear it.
> 3. Squelch. Open all the way on VFO A, tight on VFO B.
> 4. "DUP". This was a new one for me, not being familiar with the TH-D7 in
> the past. Once I figured this out, turning it on for my transmit VFO (VFO
> B), I was able to hear audio from VFO A whether or not I was transmitting
> on VFO B.
> I had to get a plug adapter to use my normal audio cable/splitter setup
> for an earpiece and my audio recorder with a Kenwood HT and its smaller
> speaker jack. I already had one for my TH-F6A, and it worked fine with
> the TH-D72A. I made sure tuning steps on both bands for both VFOs were
> at the smallest step (5 kHz), and that I had VFO B set for high power
> I started with the AO-27 pass at 2102 UTC. A very high pass here, with
> maximum elevation of 80 degrees. I worked 7 stations in 7 minutes, and
> received good reports on my audio through the satellite with the new
> radio. The only issue I had in hearing the downlink wasn't due to the
> radio - I had to move the antenna around as it passed over my head, and
> there was a moment or two where the downlink audio was less than ideal.
> I had to switch VFOs when tuning the receive VFO, something I don't have
> to deal with on my IC-2820H mobile radio or when I use memory channels in
> a non-full-duplex radio, but that was not a problem.
> The second pass I attempted with the TH-D72A was on AO-51 around 2322
> UTC. This was also a high pass, with maximum elevation of 63 degrees out
> here. I had a little bit of difficulty hearing the satellite in the first
> minute or so of the pass while transmitting, which could have been related
> to how I was holding the antenna (Elk log periodic). I found during this
> pass that I had to twist the antenna to clear up any receive issues while
> transmitting. I think I might have heard the slightest desensing during a
> couple of my transmissions, but that could have been related to how my
> antenna was oriented toward the satellite. I logged 10 QSOs on the AO-51
> pass, which wasn't bad for all the activity on there.
> As I posted earlier and said on the air, the TH-D72A is the real deal as
> a dual-band HT for full-duplex FM satellite operation. It does what the
> DJ-G7T could not do, and I didn't even have to use the expanded manual on
> the CD that came with the radio to get it set up for satellite work. I
> also set it up to work on APRS, which took little time to do. I have not
> tried it with a computer, to see if it will work as N8MH asked earlier.
> Packet is actually something I was not very interested in for this radio -
> FM satellites first, APRS next. The radio's GPS took only a few minutes
> to pick up signals when I first activated it.
> I do not have test equipment to quantify how well the TH-D72A's receiver
> is and how it compares to other radios. From playing with it last night
> and today, I know the receiver is on par with the IC-2820H I usually run
> on FM birds. Excluding transmitter power, the only thing the 2820 has
> over the TH-D72A is its separate knobs for each VFO. It also compares
> favorably with the sensitivity of my IC-T7H HT - the radio I've used on
> satellites from outside Hara Arena in Dayton (my other radios' receivers
> get swamped with intermod there, but not the IC-T7H). I will have to
> test it in a high-RF area like that at Dayton, to see if intermod plays
> havoc with the weak satellite downlinks.
> I'll work with this radio more, to get more familiar with it and possibly
> work it into my demonstrations. I will eventually get around to hooking
> it up to a computer, and seeing what I can do with packet and APRS. If
> I'm not careful, I might even go as far as having an all-Kenwood HT
> station for the OSCAR Straight Key Night in a few weeks (TH-D72A as CW
> transmitter, TH-F6A as receiver).
> Patrick WD9EWK/VA7EWK
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