Re: VARA HF Modem Speeds

Rick Muething


VARA is truly a very capable protocol and throughput on HF can exceed 20 K bytes/minute over some channels.   Tom Whiteside N5TW of the Winlink development team recently completed an extensive comparison of several HF and VHF/UHF ARQ protocols over a wide range of S:N and Multipath propagation using a new low-cost HF/VHF Ionospheric Simulator.  This kind of testing allows accurate testing with repeatable data which is often difficult or impossible to duplicate over the air. Those interested in seeing details on Tom Whiteside's N5TW simulation effort and protocol comparisons  should check out


Rick Muething, KN6KB

On 1/17/2021 5:45 PM, Tony wrote:

I observed an unusually fast file transfer while using VARA on 40 meters today (see below). It's not uncommon to see speeds of 15,000 to 20,000 bytes/minute when the band is stable, but today's observation shows that faster speeds are possible under the right conditions.

I should mention that the 30K b/m speed was recorded while receiving a 30K image.

Tony -K2MO

*** Winlink Vara Connection to KC8YJJ @ 2021/01/17 20:09:59  USB Dial: 7101.000
*** Station Bearing: 268,  Range: 393 miles
RMS Trimode
K2MO has 120 minutes remaining with KC8YJJ
{SFI = 078 On 2021-01-17 20:00 UTC}
;PQ: 44766187
CMS via KC8YJJ >
   ;FW: K2MO
   [RMS Express-$]

   ;PR: 17655197
   ; KC8YJJ DE K2MO (FN30JV)
;PM: K2MO 36Y27O2YLIPH 30887 ---
FC EM 36Y27O2YLIPH 32990 30887 0
F> C5
   FS Y
*** Receiving 36Y27O2YLIPH
*** 36Y27O2YLIPH - 33005/30899 bytes received
*** Bytes: 31145,  Time: 01:03,  bytes/minute: 29618
*** --- End of session at 2021/01/17 20:11:49 ---
*** Messages sent: 0.  Total bytes sent: 0,  Time: 01:49, bytes/minute: 0
*** Messages Received: 1.  Total bytes received: 31145,  Total session time: 01:49,  bytes/minute: 17035
*** Disconnected from Winlink RMS: KC8YJJ @ 2021/01/17 20:11:56
*** Session: 1.9 min;  Avg Throughput: 15552 Bytes/min;   1 Min Peak Throughput: 15552 Bytes/min

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