Compatibility

We test VerityRF Modem in pairs of runs. Each session is run once between two copies of VARA, and once with VerityRF Modem in place of one of them. Both runs use the same simulated channel, the same data and the same client commands. A run counts only if all the data arrives byte for byte.

Test channels. These tests used software radio channels: clean, with added noise, and with HF fading models, so every run could be repeated and compared.

VARA HF 4.9.0

PAT, peer to peer, one Winlink message each way, at 2300 Hz. The session time is from connect to disconnect. Every message arrived intact in every run.

Channel and roles	VerityRF Modem and VARA	VARA and VARA
Clean, VerityRF Modem calls	92.2 s, 10.2 B/s	92.8 s, 10.3 B/s
Clean, VARA calls	91.2 s, 10.3 B/s	93.1 s
Moderate fading, 10 dB S/N, VerityRF Modem calls	102.2 s, 9.2 B/s	98.3 s, 9.7 B/s
Moderate fading, 10 dB S/N, VARA calls	96.1 s, 9.8 B/s	99.4 s, 9.6 B/s
Moderate fading, 5 dB S/N, VerityRF Modem calls	122.7 s, 7.6 B/s	158.6 s, 5.9 B/s
Clean, VerityRF Modem sends 12 kB	191.0 s, 68.6 B/s	182.6 s, 71.7 B/s

One run per row. On fading channels two copies of VARA also vary by several seconds from run to run.

Also tested against VARA HF, with all data delivered intact:

500 and 2750 Hz sessions on fading channels, as caller and as listener, and transfers of 6, 12 and 24 kB from VARA.
VarAC at 500 Hz in both roles: chat, keep-alive pings, disconnect, CQ and beacons.
KISS broadcasts in both directions, including APRS.
Reply timing: after a control burst VerityRF Modem replies in 0.11 to 0.13 s, VARA in 0.11 to 0.12 s. After a data frame VerityRF Modem replies about 0.05 s later than VARA.
Frames and control bursts, compared symbol by symbol with VARA's own transmissions.

VARA FM 4.4.0

PAT, peer to peer, both messages, clean channel. Every message arrived intact.

Mode and roles	VerityRF Modem and VARA FM	VARA FM and VARA FM
Narrow, VerityRF Modem calls	63.1 s	62.5 s
Narrow, VARA FM calls	63.1 s	61.9 s
Wide, VerityRF Modem calls	57.8 s	57.7 s
Wide, VARA FM calls	56.8 s	57.5 s
Narrow, plus 5 kB that does not compress	99.8 s, 58.3 B/s	100.7 s, 57.8 B/s
Wide, plus 5 kB that does not compress	95.0 s, 61.2 B/s	95.6 s, 60.8 B/s

With noise and fading (one message plus 3 kB that does not compress, one run each):

Mode and channel	VerityRF Modem and VARA FM	VARA FM and VARA FM
Narrow, 12 dB S/N	89.5 s	91.2 s
Narrow, 8 dB S/N	109.5 s	110.0 s
Wide, 12 dB S/N	89.9 s	89.9 s
Wide, 8 dB S/N	109.7 s	110.3 s
Wide, 12 dB S/N, VARA FM calls	94.3 s	91.6 s
Narrow, flat fading, 15 dB S/N	111 to 113 s	120 to 121 s

Also tested against VARA FM:

VerityRF Modem's FM transmitter produces the same audio, sample for sample, as VARA FM for the same frames.
Narrow and wide stations calling each other, in both directions: a narrow link, data intact.
Digipeating: VARA FM relaying between VerityRF Modem and VARA FM, and VerityRF Modem relaying between VARA FM and VerityRF Modem.
KISS broadcasts and CQ frames in both directions, and the number of connect requests for each RETRIES setting.
VarAC in VARA FM mode (wide): chat in both directions, either side calling.

Known differences

On a clean channel VARA FM reports an S/N of 53 to 62 dB and VerityRF Modem about 44 dB. Both are well above every threshold. Through a digipeater VARA FM reports the lowest S/N of the chain, VerityRF Modem that of the last hop.
A few host-interface lines at the end of an FM link, and the position of OK after CQFRAME, differ slightly from VARA FM's.

Not tested yet

The desktop app on real Windows and macOS computers and on ARM Linux desktops. There are no macOS packages yet.
PTT hardware: CM108/CM119 GPIO, serial RTS/DTR and VOX with real radios. The PTT code has unit tests.
Speed on Raspberry Pi hardware. The ARM builds were only run under emulation.
Winlink gateways (CMS), as opposed to peer-to-peer sessions, and Winlink Express.

Keep the maximum key-down time on.