[amsat-bb] Re: more about the TH-D72A for satellites

Jim Jerzycke kq6ea at verizon.net
Sun Dec 5 21:37:28 PST 2010

Thanks, Patrick
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:
> Hi!
> 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 
> (5W).  
> 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).  
> 73!
> Patrick WD9EWK/VA7EWK 
> http://www.wd9ewk.net/
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