[aprssig] New UZ7HO Soundcard HF Packet Modem Is Really Hot!

Stephen H. Smith wa8lmf2 at aol.com
Wed Nov 16 03:08:22 CST 2011

The new, still in beta, UZ7HO "sound modem" is a sound card application that 
converts nearly any PC sound card into a high-performance dual-channel 300-baud 
HF packet modem.   This app emulates the interface of the AGW Packet Engine.  
Any program that can work with AGWpe can instantly use the UZ7HO HF sound modem 
instead.   Unlike AGW, the TNC tone pair used by UZ7HO is tunable, by clicking 
on a waterfall display like the typical PSK31 app. It has multiple software 
audio "receivers" running in parallel that tolerate off-frequency tones far 
better than other HF soft modems.

I just got back from a round trip to Chicago,  and compared the UZ7HO 
soundmodem against my "gold standard" of MixW 2.20 as a HF Packet TNC for 30M 
HF APRS from the mobile on the entire trip.

I actually operated both soft TNCs simultaneously on my Griffin Elecronics  
iMic external USB sound system, described on my website at:


The iMic was coupled to my FT-857 with the home-brew tone-keyed sound card 
interface described on my web site at:

. <http://wa8lmf.net/ham/tonekeyer.htm> .

A tone-keyed interface system like this (or the Tigertronics SignaLink) is 
almost essential when using multiple sound apps on the same sound system 
simultaneously, since multiple apps can't share the usual serial port TX PTT 
keying scheme.

Since UIview was "full up" with the TNC port occupied by the link to my Kenwood 
D700 on VHF, and the local server port was in use with the MixW connection, I 
linked the UZ7HO soundmodem to a separate program, APRSpoint, instead.  
APRSpoint (which is effectively a plugin to MS MapPoint) has native support for 
the AGW Packet Engine and also works perfectly with UZ7HO on both RX and TX.

If anyone wants to look up the raw data on APRS.fi, etc, the UIview/MixW setup 
was using WA8LMF-2, while the APRSpoint/UZ7HO setup was beaconing WA8LMF-1.    
Screen caps of both map displays during the trip are here on my website:


I thought Mix was hot as a packet modem, but this new UZ7HO modem absolutely 
blows it away!

My initial impression was that UZ7HO and MixW copied about equally well for 
stations that were EXACTLY on frequency.  For, stations more than 10-20 Hz off 
frequency, UZ7HO copied them successfully about twice as often as MixW.  As the 
afternoon faded into evening, the difference between the two softmodems was 
dramatic.   MixW didn't copy the stations on the west coast, plagued with 
multihop propagation and multipath, at all.   UZ7HO copied them consistently.  
(See the last screen shot on the page linked above.)

Having a fully-functional AGW-compatible soft modem raises some very 
interesting possibilities.   If you use AGWpe as a soft TNC on VHF,  you can 
shut down AGW and startup UZ7HO.  You then instantly have a 300 baud HF 
capability with no hardware changes at all.    This will be fantastic for 
"DC-to-light" HF/VHF/UHF all-mode radios like Icom 706s, TS-2000s, FT-857s, etc.



Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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