[BARC-List] Dxers Unlimited weekend edition 8-9 July 2006

[Dan Malloy]

Dxers Unlimited weekend edition 8-9 July 2006

By Arnie Coro

radio amateur CO2KK

Hi amigos,welcome to the weekend edition of this radio hobby program 
that is broadcast twice weekly . I am Arnie Coro , radio amateur CO2KK, 
your amigo here in Havana,

the capital city of Cuba, and I have just now completed a typical 
reverse HF band-scan... Now, do you know what I am talking about... do 
you really know how useful a reverse band scan is for both short wave 
listeners and amateur radio operators ? Are you aware that a reverse 
band scan done by an experienced operator can help to win ham radio 
contests like this weekend's IARU Radio Sport contest ? Stay here on 
this frequency , or if listening via the world wide web, keep your 
computer connected to our streaming audio, and in a few minutes I will 
tell you about the very useful and easy to

do "reverse band-scan method" to provide you with a very accurate 
picture of how HF propagation is behaving at a given moment... Item two: 
Homebrewing radios and accessories is a lot of fun, and sure,there is no 
match to the unique feeling of listening to a station using a receiver 
that you have built yourself... It doesn't matter if the radio is just

a simple tuned circuit and a diode detector or a sophisticated quadruple 
conversion, digital signal processing set... if they both were the 
product of your hard work, then they will sound better than any 
commercially built equivalent...

Take for example the many variations that are possible when you start by 
homebrewing a very well designed regenerative receiver... Of course that 
you can use it as a direct on frequency receiver as soon as it starts 
working... but the best will come when you add a crystal controlled 
converter ahead of your homebrew regenerative radio, to create a 
receiver known as a REGENERODYNE... More about the REGENERODYNES and 
several other more radio hobby related topics when Dxers Unlimited's 
weekend edition continues in just a few seconds. I am your amigo Arnie 
Coro, radio amateur CO2KK in Havana, stay right here on this 
frequency...

.......

Si amigos , this is Radio Havana Cuba's Dxers Unlimited's weekend 
edition ,and here , as promised earlier is more information about the " 
reverse band-scan monitoring technique"... Listen carefully... every 
time you connect the antenna to your receiver or ham transceiver, my 
advise is to tune the radio to the highest band of frequencies that it 
can be set... for example, a typical good quality table top receiver 
will tune up to 29,999 or almost 30 megaHertz, so when you begin your 
listening, set the radio to this frequency and start slowly scanning 
down,until you hear the first signal ...

Write that frequency down, and continue scanning downwards, until you 
find more signals... again write down

the frequency range where the first cluster of signals appears, and you 
have a really valuable information about the actual state of the 
ionosphere ! For example , Friday evening I ran the reverse band-scan 
procedure on my Grundig Satellit 800 big size , not miniature portable, 
connected to my broadband TTFD or Tilted Terminated Folded Dipole that 
provides broadband reception between

6 and 30 megaHertz.... The time was midnight local, that is

0400 UTC, and the first signals heard when tuning from my start up point 
that I arbitrarily set to 25 megaHertz, considering the time of the day 
and the present solar activity, came in at around 18 megaHertz... they 
were very weak, but careful observation led to the conclusion that they 
were certainly ionospheric propagation.... The first really strong 
cluster of signals came when the reverse band scan reached 15.5 to 15.0 
megaHertz, with by the way happens

to be a large part of the 19 meters international short wave broadcast 
band. Now, with the already mentioned data, I just apply a very simple 
formula that has given me excellent results when advising amateur radio 
contest participants...

Just multiply 15. times 0,75, again, the multiplying factor

is 0,75 and not 0.85 as usually recommended... Let's do it...

15 times 0.75 = equals 11.2, and sure enough from that frequency down is 
where stations are heard for the next two to three hours.... Its both 
simple and reliable, and you can learn how to use it by sending an 
e-mail to arnie at rhc.cu, again arnie at rhc.cu , or send a postcard or 
letter via AIR MAIL to Arnie Coro , Radio Havana Cuba, and don't forget 
to include a line saying , reverse scan method instructions, to which 
you may want also to add a reception report and your comments about the 
program.

.......

This is Dxers Unlimited;s weekend edition, and now you will be listening 
to a segment devoted to the practical , field testing of amateur radio 
antennas.

So you want to evaluate your new antenna ?

Then listen and if possible tape the program or take some notes

In order to properly evaluate the efficiency of HF Antennas is you must 
go trough a very difficult and time consuming process, if you really 
want to do a fruitful and useful test..

Listing of the number of contacts, signal reports, list of worked 
countries etc. says nothing about the efficiency of the antenna.

Many radio hobby publications describe the quality of new antennas. But 
as many of you know very well,

with just a short piece of wire connected to an antenna tuner one can 
perform worldwide contacts under good conditions, while the best antenna 
does not allow to reach any contact, if HF conditions are closed.

Also, the SWR of an antenna does not say anything about the efficiency 
of an antenna.

The SWR only tells us, how good the transmitter is

matched to the antenna, but says nothing about the radiation of waves 
from the antenna.

Based on the SWR, and following this line of thought then a Dummy Load 
would be the best antenna, as it shows an SWR of 1.0 on all frequencies 
...

The problem arises from the very different HF wave propagation, which 
shows strong variations daily, hourly, and every single minute.

A signal report of S5 may be good, while a report of S9+10 may be a bad 
report, as it all depends under what propagation conditions the report 
is obtained.

Now here is a practical procedure on how to evaluate correctly an 
amateur radio transmitting antenna system

In order to evaluate correctly an HF antenna, this evaluation has to be 
done by actually contacting distant stations.

The contact to a distant or DX station is by means of so called sky 
waves signals, waves that come back to Earth reflected by the 
ionosphere.

To make a valid comparison, we need a defined second antenna, or a 
nearby station what could be described as a comparison or reference 
station, working with the same power, and a correctly installed and 
adjusted antenna with defined characteristics.

Measuring in the near field, or in the ground wave is not suitable, as 
remote contacts work through the sky wave at an elevation angle of 
between about 5 and up to 50, 60 or even 90 degrees .

During the contact with a Distant Station, multiple changeover between 
the Test Station and the Comparing Station has to be done, to allow the 
Distant Station to dynamically make many successive comparisons of the 
signal levels of the two stations, and to perform an averaging of the 
signals if there is fading or QSB present.

This when done many times , will certainly average the results over time 
as you will always receive some "strange reports", as some operators are 
unable to read correctly the signal level, or even confuse the call 
signs.

Furthermore, you have to be really sure that the operator at the distant 
station is really reading the S meter ! YES, one has to make sure, that 
a real signal report is obtained, as many stations just report 59 
without observing the signal.

So forget about Contests for running serious antenna tests.

After performing 40 to 60 such correct test QSOs, one obtains the real 
picture of the efficiency of an antenna.

This procedure requires a real big effort, but it seems like it is the 
only valid method to evaluate the efficiency of an

HF Antenna.

And add to this that in case of directional antennas, the test antenna, 
as well as the comparing antenna have to be directed towards the Distant 
Station or otherwise the results will be obviously wrong !!!

By the way amigos , this the procedure that I have used for the past 
twenty years or so to evaluate new antennas for the HF spectrum in the 
frequency range from 1.8 megaHertz up to the top end of the 10 meters 
amateur band on 29.7 megaHertz, and all I can say is that it does bring 
very consistent and many times quite different from what you expect 
results...

......

Now here is Dxers Unlimited's very popular ASK ARNIE section of the 
program, devoted today to answering a question sent by a listener that 
is the owner of a war surplus

RAK-7 tuned radio frequency receiver... a boat anchor by

all standards, and also a museum relic... He wants to use it more, and 
asks me if it will work OK with a frequency converter, because the RAK-7 
tuning range ends around 600 kiloHertz or so... ANSWER, Yes amigo Mark, 
the RAK-7 with a frequency converter ahead of it will become an 
excellent

dual conversion receiver... a REGENERODYNE that will amaze you with its 
super selectivity so useful for picking up

amateur CW Morse Code signals... But be aware that the highest possible 
frequency for a single conversion will be

at the most the 40 meters or 7 megaHertz amateur band... so if you want 
to pick up signals on the higher ham bands like

10, 14,18,21, 24 or 28 megaHertz , you have no choice but to homebrew a 
dual conversion converter to install ahead of your very low frequency 
RAK-7 receiver that will be used

always as a tunable intermediate frequency between around 150 and 600 
kiloHertz. And please take note that the RAK-7 antenna input circuit is 
not 50 ohms, but a high impedance input designed for very short wire 
antennas...

Hope that this answers your question, and I wish you good luck with the 
frequency converter project !!!

And now amigos as always at the end of the program, here is Arnie Coro's 
Dxers Unlimited HF and low band VHF propagation forecast. Some nice 6 
meter band sporadic E openings picked up here on Thursday and Friday, 
indicating that the E skip season is still in progress... Solar flux 
around 80 units and the A index was a at a nice low level on Friday, and 
should probably continue at low levels for the next two to three days... 
Expect some interesting late evening propagation to your WEST, and don't 
forget to set your alarm clocks as early as possible in the morning to 
enjoy

the best propagation possible at this time of the year, that is 
happening from about 4 o'clock in the morning local time until about an 
hour after local sunrise. Hope to have you all listening to our midweek 
edition next Tuesday and Wednesday UTC, and don't forget to send an 
e-mail or a postcard with your signal reports and comments about the 
program ... send e-mail to arnie at rhc.cu, and VIA AIR MAIL send a 
postcard or letter to Arnie Coro , Radio Havana Cuba,
Havana, Cuba