Dear Dr. Georg N.:
Your frequency checking idea is probably beyond what my receivers can achieve.
The Zenith Transoceanic has BFO but is a "slide-rule" dial, not digital, so I never know what frequency I've got unless a station tells me.
My Sangean has very specific digital frequencies and does not show the fine +- deviations, and if it has BFO, I don't know about it among all the buttons. I'll read the book.
Interesting about German wireless law, I've never heard about that before. Looking forward to your report.
Hi Everybody!
I have not been able to work on my 13.560 MHz
AM transmitter for about 2 weeks because of
other commitments, but I will be back with more
notes and info.
Best wishes to all:
Bruce, MICRO1690/1700
Hi Everybody!
Hi Georg: I just looked at your web page again
and it is great! Are the transistors you are
using general purpose types? For instance,
a lot of experimenters I know use the
2N2222, or the 2N4401, or the 2N3904, for
instance. These are all general purpose
transistors. Do you know if your transistors
are similar (the BF494?).
Best wishes to all:
Bruce, MICRO1690/1700
Hi Everybody:
Somehow I typed two messages that are
almost the same. I cannot figure out how
to delete the first one, which is the one
I don't want.
Can you guys help me with that when you
get a chance?
Best Wishes
Bruce, MICRO1690/1700
scwis says: after a post gets a reply it's part of the thread and all that follows would be wiped out. I made your dupe posts two half posts, but if I delete this one the replies that follow would go to 🙂
Hi to everybody,
my radio web page is going to move to another domain.
It's name is already officially registred:
www.radio-hobby.de
I'll be back one of the next weeks with more news after making some investigations into german law and transistors.
There is an idea about an AM modulator which increases transmitter (carrier) power with increasing intensity of modulation, and which decreases the carrier when modulation pauses. I already tried this (with some other low-power transmitter circuit) and it works. For reception, you can use a normal AM receiver.
Yours, Georg N.
Hi Georg:
I think the kind of modulation you are
describing is known (around here at least)
as controlled carrier AM. That sounds like
a great idea!
Best Wishes:
Bruce, MICRO 1690/1700
Dr. Georg N. asked what kind of antenna is used for measuring the transmitter output radiation.
The Part 15 FCC U.S. Regulations for this frequency permit ANY type of antenna of any length, so long as the allowed signal strength is not exceeded!
15.225 (a) The field strength of any emissions within the band 13.553 to 13.567 mHz shall not exceed 15,848 microvolts/meter at 30 meters.
My test antenna is merely an overhead horizontal wire run through several rooms indoors. It's been too cold or wet to build an outdoor antenna, and I don't expect it to be easy, especially with no tall tower or other high structure.
I'm going to put a dipole in the attic for now.
Best Wishes
Bruce, MICRO1690/1700
Thank you for fixing up my messed up
posts and the explanation of how it works.
Best Regards
Bruce, MICRO1690/1700
Dear Bruce, Micro 1700,
sorry to say, but there is no similarity between BF494 and any of the mentioned 2N2222, 2N4401, and 2N3904. Generally, 2N4401 is similar to BC337, and 2N3904 is similar to BC549B, and all are low frequency types, whereas BF494 is a medium frequency type. Thus: too much different. However, the 2N2222 seemed to be interesting to me. I tried it here, but: Especially the DC current gain of BF494 is two times higher than that of 2N2222. Even more important: the internal capacitance of BF 494 is very low at about 1 pF, that of 2N2222 is much, much higher, and this interfers with the frequency, since it produces a lot of unwanted phase shift. Last, but not least, the transit frequency of BF 494 is lower, which may be important if you don't want wild oscillations. For the experimentator trying to get a good result from the home-made RF-circuit, it may be better not to interchange different transistor types (If you want to reproduce my circuit, I recommend not to change anything, the circuit is a little bit critical because of the radio frequency). O.K. if you look again onto my radio-hobby.de page, you will find the final version now, together with an AM modulator, and following your suggestions I use an american type transistor 2N2219A in the final stage. I must confess, the power of 10 Milliwatt is very low, but on the other hand side, the signal is "clean".
Dear Carl Blare,
what I intended to ask is not the transmitter antenna. I had the idea that I could use my radio as an apparatus to measure the field strength, and of course this apparatus must have a reception antenna in order to measure the field strength. If I want to do so, I need some accurate mathematical or physical approach to the relationship between field strength (~15 µV/m) and voltage at the antenna of my measuring apparatus. Perhaps there is someone who knows, which voltage (µV) is expected at the connector of a lambda-half dipole (or any other antenna type) that is situated in a field of 15µV/m.
Yours, Georg N.
Dear Dr. Georg N.
What you are asking has been discussed somewhere on this site, and I think uses the example of the equipment used by the FCC field inspector. I expect that soon a knowledgeable person will link us to that information.
Hi Georg:
Thank you for the information and the
detailed explanation about the
transistors. I tried to look at your web page
but it did not appear here. Maybe I did
something wrong.
I will try to look at your web page again soon.
Thank you and Best Wishes
Bruce, MICRO1690/1700
Hi Bruce, MICRORADIO 1690/1700,
hope it works from USA. Here I had no problem to get the site on the PC screen. But please give me a note if the page continues to make problems. Thank you.
Dear Carl Blare,
you asked "what kind of power regulations govern you in Germany". I wrote to the authority. I think the answer will need some time.
Best wishes, Georg N.
I get your website now!
Beautiful job!
Best Wishes
Bruce, MCRO1690/1700