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Re: [HCDX] Dxers Unlimited script weekend edition July 14-15
DXERS UNLIMITED
Dxers Unlimited’s weekend edition for July 14-15 2007
By Arnie Coro
radio amateur CO2KK
Hi amigos radioaficionados around the world and also those of you now in
space orbit around the Earth … I am Arnie Coro, your host here at Radio
Havana Cuba’s twice weekly radio hobby program… It’s certainly nice to
have you listening to the show, and I hope you enjoy every minute of
it…Your comments and ideas on how to make Dxers Unlimited a better
program are most welcome at my direct e-mail address : arnie@xxxxxxxxx
Now here is item one, very low solar activity continues …
Sporadic E propagation reports continue to come in from North America,
Central America and the Caribbean, as well as from Africa and Europe.
Recently received e mail messages talk about excellent VHF bands
openings, and one particular recent opening that took place on the 6th
of July, reaching maximum useable frequencies up to the 1.25 meters or
222 megaHertz amateur band, that made them lots of VHF operators very
happy indeed, as this was their first ever opening on 222 megaHertz, and
for some other newcomers to VHF Dxing, their first two meters band
opening via the ionosphere …
The extremely high free electron density at the height of the sporadic E
layer also made possible TV DX signals on NTSC channels 7 to 13 , that
operate from 174 to 216 megaHertz.
Sporadic E openings are expected to continue during the next several
days, and some of them maybe happening even during the late evening
hours.. I do insist that there seems to be some sort of relation between
periods of very low solar activity and sporadic E events !!!
Item two today, will be our Technical Topics section, then item three
time slot is for ASK ARNIE, and the pending visit to my workshop will be
the fourth item of this program that will come to an end with our
exclusive and not copyrighted , in the public domain HF plus low band
VHF 30 to 60 megaHertz propagation update and forecast.
I am Arnie Coro, radio amateur CO2KK, your friend in sunny Havana,
together with my sound engineer and producer Jose Costa Pupo, both of us
ready to continue providing you with the most up to date radio hobby
related information, as the weekend edition of Dxers Unlimited continues
in a few seconds..
;;;;;;;
Si amigos, your radio is tuned to one of Radio Havana Cuba’s English
language broadcast frequencies, this is Dxers Unlimited, our twice
weekly radio hobby program, and here is our TECHNICAL TOPICS section of
the show.The cascode regenerative detector circuit presented here at our
mid week edition brought a lot of e-mail requests for the 40 kilobytes
file in dot jpg format that shows the schematic circuit diagram of Udo
Peter’s unusual radio receiver… Several listeners have asked for more
details of this circuit, so here they are/// in the first place, be
aware that the cascode regenerative detector was built using a dual
triode vacuum tube, of which there are many types that can will perform
nicely in this circuit, but, if you don’t have a dual triode in the same
glass envelope, just use two identical triodes,and the circuit will work
quite well also. Among the triodes tested here in my prototype are the
12AT7 or ECC81 ,that has proven to be an excellent performer, the 12AU7
or ECC82 that showed somewhat less gain as the frequency to which the
radio was tuned went up but worked very well up to around 15 megahertz
or so, as a 12AU7 according to the vacuum tube manuals is nothing but
two 6C4 triodes packed inside the same glass envelope, and also tried
out the ECC85, of which I don’t remember its American standards
designation, and that proved to be the best performer, providing
excellent sensitivity on the 27 megaHertzs Citizens band, a frequency
range that is usually very active when sporadic E propagation events are
in progress. I was able to pick up lots of Citizens Band skip signals on
AM, and even some of the many so called OUTBANDERS, that operate between
the top end of the Citizens band and the beginning of the 10 meter band,
that is from about 27.4 to 28 megaHertz… Another interesting finding
when experimenting with the cascode detector regenerative receiver was
that changing the values of the first triode’s grid resistor and
capacitor had a significant effect on the performance of the radio !!!
Using typical values for classic regeneratives, like 100 picofarads and
1 megaohm , provided inferior performance, and the radio’s sensitivity
and selectivity improved considerable when the value of those two
components was changed to 22 picofarads for the capacitor and 10
megaohms for the resistor… My advice is that you aim at using the
highest possible quality component for that capacitor, because there is
no doubt that it is vital element of the circuit. The other component I
talked about during the midweek edition of Dxers Unlimited, was the
regeneration control potentiometer, and again, let me insist in the fact
that it is extremely important to use a very high quality potentiometer
, in order to obtain a velvet smooth control of the regeneration that is
free of any noise generated by the wiper of the potentiometer…. So
amigos, there you are again, learning about a unique radio receiver
circuit, the cascode regenerative detector, that has proven to be an
experimenters dream !!! Again, the circuit diagram is available via
e-mail, just send me your request to arnie@xxxxxx, it’s a small dot jpg
file, just 40 kilobytes,and I will soon follow it with a text file that
will summarize all my experiments with this unique circuit, that has
left all my visitors here at CO2KK’ s shack absolutely amazed… as a
matter of fact , I had to print more copies of the circuit, as everyone
coming here to my workshop seems to want a schematic diagram, after
listening to the prototype !!!….Again, in case there was a little QSB ,
that is fading of the short wave signal,
I have here the circuit diagram of the new cascode regenerative receiver
built by Udo Peters in Germany, It is in dot jpg format and it’s a very
small file, using only 40 kilobytes, so it can be sent as an e-mail
attachment to Dxers Unlimited listeners around the world that want to
see it. By the way, the only electronic component used in this
interesting design that may be hard to find, is a 56 volts Zener diode
regulator, that is feeding regulated voltage to the detector… Something
that I have solved in two very practical ways, in one experiment, I used
two 24 volts Zener diodes in series,or four 12 volts Zeners , and in
another one, I used a Vr-75 glow discharge voltage regulator tube, in
the case of the series connected Zeners, there was no need to modify the
circuit, but in the case of the VR-75, I had to increase the value of
the series resistor connected to the hot end
Now, here is ASK ARNIE, Dxers Unlimited’s most popular section…
Answering today a question sent in by another long time listener , from
Canada… Amigo Gerry is asking a very interesting questions about UPS
units, uninterruptible power supplies, that by the way, are ideal for
handling amateur radio emergency communications by doing a very simple
modification to the UPS units. Gerry wants to know if he can connect two
UPS units to increase the available operating time when the electricity
supply fails, and the quick answer amigo Gerry is NO, for many technical
reasons… among them the fact that not too UPS units built by the same
manufacturer are identical… My advice is to obtain a large sized
battery, and connect it to the UPS unit by means of heavy cables and
proper protection devices, and by that I mean fuses and a fast acting DC
circuit breaker. For example, if you connect a heavy duty marine type
deep cycle battery with a capacity of 180 ampere hours to a regular 450
volt ampere UPS unit, the system will be able to provide your emergency
communications station with power for a very long period. You can
optimize the emergency supply by connecting the radios that use 12 volts
DC directly to the deep cycle battery, and other equipment that uses 115
volts AC to the output of the UPS. I hope amigo Gerry that you
understand that heavy current DC circuits must be dealt with very
carefully, as poor connections could lead to overheating and even may
start a fire !!! So be extremely careful when working with direct
current circuits that handle many amperes amigos.
Then, here is the second “ trick” about UPS units… you can simply dig
inside, find the wires that go to the internal rechargeable battery, and
install two heavy duty binding posts , so that you can use the internal
battery to provide power to your radios that use 12 volts DC. You don’t
even have to turn on the UPS unit to operate your radios, and this is
something that can be done very easily, but don’t forget to include a
heavy duty fuse holder and a fuse of the right current rating between
the battery and the external connections. Here at CO2KK my amateur radio
station, I have modified two old UPS units, and they are now doing
tripple duty, as battery chargers, external DC power supplies and of
course, their intended primary service as uninterruptible power supplies
for computers.
Keep in mind that one of the reasons why amateur radio exists is that it
provides emergency communications second to none, so everything you do
to keep your amateur radio station ready to handle emergencies is a step
in the direction of assuring the future of this aspect of our wonderful
hobby : RADIO !!!
……
Arnie’workshop today as crowded as ever, with no less than three radios
waiting for repairs, and the micropower QRP rig connected to the dummy
load with the key down to test its reliability… One of the radios to be
repaired hopefully this coming week is a very interesting set, that
forms part of a field intensity meter, covering from 30 to 300
megaHertz… Seems like a capacitor in the power supply failed, and the
radio is providing audio output with a very high hum level… Repairing
radios , new and old, and even antique ones, is one of the more than 81
ways that you and I enjoy this fascinating hobby amigos !!!
Now , as always at the end of the show, here is Arnie Coro’s Dxers
Unlimited’s HF plus low band VHF propagation update and forecast.
Solar activity expected to continue to be at very low levels during the
next several days. No significant sunspots regions on the far side of
the Sun, and the same holds for the visible solar disk. The effective
sunspot number has hovered at very low levels, and the recent fantastic
sporadic E opening might be somehow related to this marked minimum in
solar activity indeed. Solar flux is now around 80 units and moving
steady up, expect solar flux to be around 80 units by mid week. The
effective sunspot number near 25, , and we do see the effective height
of the F2 layer reaching up to near 400 kilometers above the Earth’s
surface at locations where the Sun is high above the horizon, something
that makes daytime HF propagation conditions very poor indeed. !!!
AND PLEASE… don’t forget to send your QSL card requests, radio hobby
related questions and any ideas you may have to improve the Dxers
Unlimited, so that it can be a better program to serve you and all the
radio enthusiasts around the world !!!
Send mail to arnie@xxxxxx, or VIA AIR MAIL to Arnie Coro, Radio Havana
Cuba, Havana, Cuba
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