> ?downloaded IEC 315-1 standard. Item 20 - "Antenna Simulation Networks?
> Artficial Aerials )" basically covers three type of antennas: open-wire?
> antenna 100 KHz - 30 MHz, rod and telescopic antennas?
The above comment made me realized the Indian version is far less descriptive than my photocopy of the (cutthroat) original. IMHO, the missing information renders the Indian version useless. So, please view the following:
> I found in IEEE Standard, 1961 the details about the?
> recommended dummy antenna impedance that mimics?
> open-wire antenna: Za=1500 Ohms @ 500 KHz, 200?
> Ohms @ 2 MHz and 400 Ohms @ 10 MHz.
?
Can you kindly point me to the document? Thanks.?
?
> I thought Steve Ratzlaff did some "unpotting" amongst others
> Maybe we need to find out what they found.
> I remember seeing results from at least two "unpottings"
> I would think an optimized impedance matching over a relativity?
> large frequency range was super critical.
?
Martin's website (now defunct?) pointed to .?According to the teardown, there is no LPF in the Wellbrook amp, save for a pair of 82 pF caps at the input. Hence, there's NO impedance matching at the input that tracks the loop impedance changing with frequency. AFAIK, only LZ1AQ with its LPF has an input impedance that track the loop's - albeit a "happy accident" in Martin's word.?
Additionally, the Wellbrook teardown showed two pairs of anti-parallel 1N4148 at the input which would have made Owen Duffy sneered in disgust :-). Read Duffy's scathing dismissal of "diodes connected to antennas": ?
Duffy's concerns over PN diodes (e.g. 1N4148) causing intermodulation can be addressed by substituting with long lifetime PIN diodes. So, as (ex) application engineer for PIN diode limiters for over 2 decades, I must lend my wholehearted disapproval, too! :-)?
?
> Ikin knew all that decades ago !!!!!!!!!!
?
I do NOT relish in building and evaluating so many designs - LZ1AQ, PA0FRI, M1GEO, & MLA-30, etc. So, if someone can furnish me with quantitative data showing that Ikin's Wellbrook is the undisputed performance leader, then I will throw the other designs out of the window and fully embrace the Wellbrook! :-)
Digression: Almost all active whips have high input Z. Interestingly, there is contrarian design which sports low input Z using feedback in order to achieve high IP3 (53 dBm). Hmmm... low Z like LZ1AQ minus the LPF :-)
https://analog-electronics.tudelft.nl/downloads/NordholtActiveAntenna.pdf
