Wednesday, April 22, 2020

cw transceivers

Problems:- 

I enjoy home brewing. When project  takes too much time in development , board is finished but i do not have other necessary technologies, to wrap up the things i box them up as it is. later on, when time comes ripe, i use these boxed-device after lots of changes. I am rejuvenating one of that transceiver project. That was made few years back. That was never tried on air nor their air worthiness checked.

Our ham station must have some air worthy transceiver.

On impulse of coming to air, few months back tried to make the 21168kc xtal based cwtx-dcrx transceiver but the xtal was 3rd harmonic one. It was not usable on 15 meter and did not liked to use it on the 7056, So i tried the 21096 in the same platform. RX was good sensitive but the irf 510 is not producing enough umphhhh.  Need to redesign the cw tx chain with 2n3866, 2n2078 etc a big work. not doing. abandoned the 15meter for now.

Then i remember in last to last lamington road electronic market, mumbai visit i had bought the 10 number of 3686 kc xtal.  I placed this 3686kc xtal in this modules and there  was RF ,light in the lamp load. WOW.  It might be producing more than 2 watt RF power. workable. This RF power can drive external linear. good. or it should be usable for local com. hope so.

I am becoming old without any contact. Story can be depicted " unused old stock but brand new in package". he he. Why we should re-invent new new platforms for each receiver and transceiver. I am really tired of making separate seperate receiver, transmitter, transceiver for different different bands. A thought was puzzling me, can't we make something that is workable, usable , reproduce-able and worth every cent of that dollar spent ? This  trx making is costly, time consuming, tedious task.

We need one unit with 3-4 bands, even if it is xtal based, DC receiver and CW / DSB transmitter. We must have at-least 2 to 5 watt. this can be put in small box ( samilar as MTR3-B ) and an external 20 watt linear for reliable communications.

Solutions:-

There must be some solutions. Then i searched my xtal storages boxes. i found this 6 xtal sets. All these are in ham-band. and does not fall into any popular crowded net.

meter band =  tx freq crystal = poliakov rx freq crystal
80 meter band = 3686kc = 1843kc
40 meter band  =7159kc= 3579kc
20 meter band= 14318kc=7159kc

So with one cw tx board, band switching and using the poliakov dc receiver using sub-harmonics oscillators i can make three band portable transceiver.



Good idea.When you are making new device, Plan it right as time is finite. Make airworthy, use whatever you have, operate on cw ,then modify for DSB fone. RX front end should have good band-pass filter. there should be wide/narrow AF filter. there must be RIT. Easy tx-rx change over. There should be RF-indicators. And VSWR antenna tuning. side-tones makes it perfect. just have a look at vk3ye.com and youtube for his work and idea in cw qrp.

So work is in progress when its finished will reveal here with a different write-up. 

And yes, i will be QRT with twitter, facebook social media . also not recharged the mobile-fones internet as no work no money due to corona epidemic.

Straight keying morse is a very tiring work so, i will make arduino automatic cq caller. cq cq cq de vu3inj vu3inj k. Please scan the band. you might catch me on 14315kc, 3686 kc calling cw. Send the SWL report and i will reply with handmade QSL card. i will reply very very short "ur rst 5nn bk hw cpy ? "
73
vu3inj
indrajit.
click here to see " 3686kc transceiver " on youtube.

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