ESP32 HF QRP FT8 Transceiver

The whole transceiver is enclosed in a 1.5 mm aluminium box, which is very good for EMI shielding but very bad for the WiFi link. When I shut the cover, WiFi signal level drops down and becomes unstable.

I guess two options:

• an external WiFi antenna (pretty easy)

• an Ethernet link (pretty daunting)

About 15 days ago I succeeded to follow this almost correct FT8 sequence, but it had a few issues.

Issue
I decoded HB9DGZ answer -05 at 20:05:37 but its transmission was since 20:05:15 till 20:05:27 (my decoding took 10 seconds). 

Therefore (waiting for the even slot) I could plan to send R+06 only 1 minute later, since 20:06:30 till 20:06:42. 

In the meantime HB9DGZ, not seeing my reply, correctly retried answer -05 since 20:06:15 till 20:06:27 which I decoded at 20:06:36. 

At last, at 20:06:30 till 20:06:42 I transmitted R+06

Promptly, HB9DGZ decoded R+06 and transmitted RR73 since 20:06:45 till 20:06:57, which I decoded  7 seconds later at 20:07:04

My upgraded sequence

I answered SV9TLU transmitting JN53                        since 9:33:00 till 9:33:12

At 9:33:15 SV9TLU transmitted -06 to me                    since 9:33:15 till 9:33:27

I decoded -06 before 9:33:30 so I could answer R+06 since 9:33:30 till 9:33:42

Final consideration

Since last SV9TLU CQ (at 9:32:57) till its RR73 (at  9:33:57) elapsed only 1 minute

To see my software improvements, see my my Github

After a few attempts I was able to follow a correct FT8 QSO sequence, as you can see here.

After finishing the RF amplifier and mounting it on the inner side of the aluminium box top, I can say the hardware assembly is quite consolidated.

The RF amplifier is on the left, with the two RD16HHF1 in push pull screwed directly on the inner side of the cover (below the perfoboard). 

20260406 20:48:00 CET

With this receiver connected to my 10-160m mutilband End Fed Long Wire antenna I can receive a lot of FT8 spots from all over the world. 

I was the only one, in Europe, to receive a message from KH6DL over the last 24 hours.

My antenna is nothing special as it's located at about 6 meters from the ground, between some buildings. Therefore I think my receiver is not so bad!

Mar 28th 2026

This morning I tested a single CQ IW5ALZ JN53 transmission (8W)  and I got:

In the web portal I added a spot (on the left) and QSO (on the right) decoder:
 

(TODO) You could answer a CQ directly pushing Answer CQ.

I start from the SI5351 CLK2 signal, which is a (more or less) square wave with an amplitude around 3 Vpp.

At the moment I've built a 0.5 - 1 W amplifier (1-30 MHz 0.5-1 Watt class C amplifier) which works pretty well, but I'd like to reach 5 Watts at least.

For this reason I'd like to replicate this schematic  

that I found here 20w-broadband-hf-1-55mhz-power-amplifier.

I modified only the voltage control part, using 2 bjt's instead of 2 MOSFET's because I have no P channel MOSFET.