Dr. Ulrich Rohde: Electrically Short Antennas

You may have a point; If you mix a German, an Italian and an Indian in a presentation the English may suffer, but I hope the technology came across ok .
Sorry for that,

 

Thanks for posting these papers.
Your humble reply's are refreshing.

I'm still trying to get my arms around Electrically Short Antennas.
Could you say that as the electrical length gets shorter that the usable bandwidth gets wider?
As it gets shorter will it start to have the effect of cutting off the low freqs? (ie High Pass Response)
Does this have the effect of flattening the freq dependent path loss slope?

Thanks again for posting this.
73 de Dale

 

Please send me your telephone number via email, ka2weu@aol.com and I can explain you the theory much better then here... Ulrich

 

That would be awesome!
I just sent you an email.
Dale

 

It's actually pretty easy as long as you consider the source. Those folks with titles like Ing., or Dr. Prof., or have initials like EE or PhD behind their names usually know of what they speak.

 

QRZ members are fortunate to have these members who are willing to enrich our knowledge base.

 

We are fortunate to have them. My comments weren't to discredit anyone in this thread but there are some people on the internet that spread bad information. Some of them have letters behind their name and don't mind telling you about it. 73

 

I have been CW only for 62 years.
Working CW is like Navigating by the Stars!
Even after many years of college,
I am still a believer in the Reality of Analog Signals.

I tell my digitally oriented ham friends
that
(1) the Real World WAS Analog in the Beginning,
(2) the Real World IS Analog today,
(3) the Real World Will BE Analog forever.
and that
all the Digital Signal Processing "DSP" circuits
receive "Analog-to-Digital" processed information
and thus DSP becomes only Data Processing.

Thank you for speaking about
the Natural Analog Signal as a fundamental fact
which is distinct from the DSP developments.

Interesting topic !

 

I, for one, would be very interested in such a white paper. I have been an electronics designer for decades and also made some "trips" to the DSP world, enough to understand the pro's and the con's but still learning. And I have always had this idea in my mind to build a receiver just for fun, without compromises or sacrifices for cost. Just because I could. And I think many hams would/could do this. Indeed, many products on the ham market are a compromise between cost and performance. As a hobbyist, noone is going to fire me if I wanted to spend $200 on a front end, knowing that it would be the best that could be achieved with the highest IP3 numbers and 0.1dB NF, so to speak. I could see a benefit in the perfect marriage between analog and digital in such an H/SDR.

(oh, and a happy and healthy new year, by the way)

73 de Meindert - PA0MHS

 

Good morning,

Thanks for the reply. So in a week or so I will put a paper together to show and mathematically demonstrate the optimum solution. A lot will depend on the target bandwidth and the noise figure, actually the most complicated point will be a 70 cm version and also there will be a difference if continues coverage is needed or “only selected bands”.
There also is a difference between an communication SDR and a monitoring/surveillance receiver with a very high instantaneous bandwidth. There will be lots of similarities between this approach and a high end spectrum analyzer including the ability to store a bursts signal and its analysis later.

73 de Urich, N1UL

Ps: I hate this spell checker , it adds last minute mistakes !

 

I am also looking forward to such a paper, preferably written from the
systems engineering perspective.

It should be stressed that it is not possible to optimise everything at the same time, and that "no chain is stronger than its weakest link".

By knowing which parameters influence the end result the most and how the interrelate, it becomes possible to make better informed decisions when designing and assembling a complete system.

73/
Karl-Arne
SM0AOM

 

In simple terms, you are correct, As stated you need to be able to switch between communication mode ( frequency hopping, spread spectrum and added crypto mode ) and frequency monitoring/ direction finding and before you know what happened you will be above $ 100000.
My current location provides line of sight into NY city with many signals of up to 0 dBm, mostly broadcast stations and cell phone and trunking systems. And to be able to listen to 2m and 70cm SSB stations like a few hundred miles away is a huge technical task.
Take a look at my website N1UL.com .

73 de Ulrich

 

I would like to see such a paper as well!
It seems to me that for a communications mode receiver it would be ideal to have a frequency and bandwidth agile filter on the front end. And setting the bandwidth equal to the information bandwidth.
This can be done easily in DSP so maybe the money should be spent on the ADC.
What is the P1dB of the first mixer vs the P1dB of the ADC?
Just linking out loud.

73
Dale