Re: [HCDX] Dxers Unlimited script weekend edition July 14-15

["Prof. Arnaldo Coro Antich" <inforhc@xxxxxxx>]

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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