Radio Havana Cuba
Dxers Unlimited - for Tuesday 26
February 2019
Arnie Coro, CO2KK
The Cuban CW Group of amateur radio operators is
promoting a project that will help both beginners and experts operate on CW
Morse Code Radiotelegraphy mode using a simple low power transmitter... Two
versions of the low power rigs are now in the early design stages, one using
all solid state devices recycled from retired computer CRT monitors and TV
sets, and the other a hybrid transmitter using low power transistors and a pair
of also recycled vacuum tubes operating as the driver and final RF amplifier
stages.
But, Jav, CO3JK, charlie oscar three Juliet Kilo, the Secretary of
the Cuban CW Group wrote an e'mail explaining that the first part of the
project aims at building a rugged, reliable power supply for the transmitters.
More radio hobby related information coming direct and
from the source... in a few seconds after a short break for a station ID, I am
your host Arnie Coro, CO 2 KILO KILO in sunny La Habana, Cuba enjoying
wonderful early spring weather...
Si amigos this is Radio Havana Cuba... the name of the
show is Dxers Unlimited and here is now more radio hobby related information...
a few days ago I decided to dismantle an old hybrid amateur radio transceiver
that had broken down many times , making each time more and more difficult to
repair.
It was not an easy decision, but when I started to take the rig
apart, it proved to be the correct thing to do, when after testing the first
ten electrolytic capacitors removed from the Kenwood TS820S using an equivalent
series resistance meter, they all proved to be totally out of the minimum
parameters... Attempting to revive that rig without a supply of high quality
fully tested electrolytic capacitors for both the high voltage and low voltages
power supplies would be simply an impossible task and it will also require a
tremendous amount of time.
Another finding that came out during the first
steps of the dismantling process was related to the type of wrap around
solderless connections used by Kenwood, that in my opinion was a very poor
choice by the designers... The rest of the story is that so far I have
carefully removed the VFO assembly, and the big power transformer that
will soon be used for other home brew projects... Other small parts will need
to be removed by first extracting printed circuit boards where valuable parts
like the single side band filter and many quartz crystals can be recovered for
recycling.
Needless to say the Kenwood TS820 S had provided a useful service
life of several decades that could had extended further more if a
different method of assembly had been used... An before I forget the
radio frequency driver stage and the two beam power tubes power amplifier were
also neatly removed and could be used for a simple single band rig, making good
use of a power supply built using the big transformer recovered from the
transceiver.
ASK ARNIE, la numero uno, the most popular
section of Dxers Unlimited is now on the air... answering a question sent by
listener Salvatore from Romen , Italy... Amigo Salvatoreo wants to hear my
opinion about the possibility of building self excited power oscillators for CW
that use the Hartley – Hull circuit... Well amigo Salvatore, all I can say is
that it can be done, but it does require the use of some hard to find parts,
like wide spaced air variable capacitors , that are essential to achieve the
required frequency stability, and you will also need a very stable fully
regulated supply to feed the power oscillator.
My very good Italian friend Cris Greggio has built a
prototype Hartley Hull single stage power oscillator that sounds very good on
the air and does not drift at all. I remember many years ago building a similar
CW rig using a single triode connected 807 type tube , fed from a professional
high voltage regulated power supply... It provided about 15 watts output on the
40 meters band and was really stable ... Keying was excellent and no chirp was
heard from that rig... Using an also home brew regenerative receiver, the 807
triode connected power oscillator made possible making some very nice DX
contacts, but I must add that this happened many years ago during solar cycles
20, 21. 22 and 23 that were much more active than the present very weak cycle
24...
Soon, Radio Havana Cuba will be changing to
the A19 transmissions schedule... and very few changes are expected to take
place... The reason for not having to change many frequencies has to do with
the very low solar activity expected for this season that starts during the
spring and comes to an end during October.
.You can send your signal reports
and comments about our short wave broadcasts to inforhc@enet.cu, again inforhc@enet.cu, and don't forget to include details of the
programs heard so that we may verify your reception reports with a nice QSL
card....
More radio hobby related information coming up: Recent
radio noise measurements done at several of the world's most populated cities
and also done at smaller towns and villages show something in common... The
general background radio frequency noise levels within the frequency range from
three to thirty megaHertz has increased dramatically during the past five years
where ever measurements made five years ago were available...
The results of those
carefully done bandscans measuring the background noise demonstrate that
services that once where capable of providing good quality coverage like the AM
medium wave broadcast band have become, at some urban locations almost useless,
even when the stations are using high power transmitters .... Add also that the
FM broadcast band is also suffering from many electromagnetic incompatibility
problems that reduce the service area of many stations in a significant way....
And now just at the end of the show,here is Arnie Coro's
Dxers Unlimited's HF propagation update and forecast, expect poor to very poor
conditions during the next two days due to the likely to happen effects of a
high speed solar wind stream coming from a coronal hole... All I will recommend
is to monitor the lower frequencies for possible propagation anomalies...
Send
your signal reports and comments via AIR MAIL to Arnie Coro, Radio Havana Cuba,
and use our primary e'mail address inforhc@enet.cu .See you at the
weekend edition of Dxers Unlimited on the air next Sunday and Monday UTC days,
