This is why I brought up the TH-F6 which is not purpose built for data. Though it does have a TNC setting in the settings menu for external TNCs.?
My setup for Vara FM on the go is :
Windows 11 Surface GO2 tablet with USB-C connector, connected to a DigiRig that then connects to any of those 4 HTs I've mentioned. ?I regularly use one of 4 local mountain top digital repeaters, two are Vara capable and two are only Packet (they run on Linux servers). They are all less than 14 miles away and are all on mountain tops. I live in the SF Bay Area and we are surrounded by mountains.?
The HTs are all 5W or less (most often less because I don't use external power supplies while I'm out.
The antennas I'm using on the HTs are either stock or BNC attached HT antennas. I also have a Ed Fong ?multi-band rollup antenna that I keep in my bag to put up in a tree or something.?
My home setup is a Windows 11 VM running on a Mac that is also connected to a DigiRig... The radios I most commonly use here are either a Kenwood TM-V71, TM-D710, or a Yaesu FT8800. ?Though sometimes I use an Icom 705 at 10W. The Icom has a built in sound device, so no digirig there is necessary.
The antenna I use at home is either a comet base vertical OR the Ed Fong rollup.
I also use a TNC3 or TNC4 for both APRS and Packet and they are capable of connecting to any of the above radios.
So, while I don't and won't consider myself a digital guru or as experienced as most, these are the radios and devices I use and have regularly been able to check into the Winlink Wednesday net with all of the above radios and setups and have been doing this for over a year now.
The reason I do this is I'm a big fan of testing my equipment for those rare occasions where I wish to be able to send messages or emails in an emergency. ?Every HT I buy and use has to be capable of doing packet or vara.
73 de K6EF
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On Jul 9, 2023, at 9:11 AM, WA8LMF via groups.io <wa8lmf3@...> wrote:
On 7/9/2023 10:35 AM, Mark Cohen via
groups.io wrote:
I
actually disagree. I have many HTs such as a th-d72, th-d74,
th-f6a, and a ic Id-52a. All of which work just fine with either a
digirig or a mobilinkd tnc3/4. All work with either the stock
antenna, after market antenna or externally connected antennas ?
The Kenwood TH-D72 and D74 are the rare
exceptions among hand helds in that they are actually
purpose-built for data.? The RX-to-TX and TX-to-RX turnaround
times are optimized for data to support the built-in TNCs.? I
don't know about the others you mention.
You must have a remarkably clean unobstructed
path to the digipeater or other station if the on-set antennas
actually work for destinations more than a few miles away.? Or
you have the western scenario of digipeaters on mountains
THOUSANDS of feet above the users, yielding a true line-of-sight
low-loss path over long distances. ? Or the digi is sited on a
TV broadcast tower HUNDREDS of feet above ground level.?
Normally, any kind of? on-the-set? antennas
are going provide NEGATIVE gain, due to the radio chassis being
too small to provide a decent ground plane/counterpoise to the
whip.? (On two meters, the radio chassis would have to be 19"
tall to be a decent ground to the whip.)? The "rubber duck" or
other whip may be tuned to match the 50-ohm output of the
transmitter -- but the radiation pattern is mostly skewed up in
the air? instead of straight out at the horizon.?? The only
exception would be end-fed half-wave antenna designs which are
38" tall on 2M.?
FURTHER.....
Traditional 1200-baud packet/APRS uses audio
frequency-shift keying of a single sine-wave audio tone. Simple
AFSK can tolerate a lot of audio distortion and uneven frequency
response in the TX and RX audio systems, and still work. ?
ON THE OTHER HAND...
VARA uses multiple QAM (quadrature amplitude
modulation) audio subcarrier tones SIMULTANEOUSLY. This kind of
very-complex wave form is FAR FAR less tolerant of audio
distortion, uneven frequency response and over-driven transmit
audio limiters in the radio, than the simple single-tone
sine-wave modes like AX.25 packet or SSTV.
??? Audio Inter-modulation distortion (a.k.a. "IMD") in the TX
and/or RX audio stages takes the original multiple tones and
adds/subtracts them to/from each other, creating numerous
additional audio frequencies in the pass-band. All this
additional "trash" in the audio pass-band then makes decoding
the original tones much more difficult.? Note that this kind of
IMD can happen either in the transmit audio chain, or in the
receive audio chain if levels are set too high.
??? Transmit audio level setting is very critical on modes like
VARA -- You MUST keep the TX audio level low enough that no
clipping or IMD happens in the TX mic amp and modulator chain.
??
??? (This is the reason for the complex "auto-tune"
trial-and-error level-setting feature in VARA. If you have a
communications monitor with a modulation scope, you don't need
the auto-tune process -- you can instantly see if the audio wave
forms of the transmitted VARA signal have clipped flat tops
instead of a mass of smooth rounded over-lapping sine waves)
Stephen H. Smith???
wa8lmf (at) aol.com
Skype:??????? WA8LMF
EchoLink:? Node #? 14400? [Think bottom of the 2-meter band]
Home Page:?????????
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