Search found 635 matches

by glovisol
Sat Jul 06, 2019 3:08 pm
Forum: General
Topic: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF
Replies: 8
Views: 1143

Re: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF

3.3 WIDE BAND PRE-SELECTORS - FIXED BANDPASS FILTERS @ 3.8 MHz - PRACTICAL IMPLEMENTATION Figure 5 below shows the detailed practical implementation of the 3.65 MHz pre-selector, with air core coil technology, compared to Powder Iron toroid technology. At this frequency, due to the higher Qu's, Pow...
by glovisol
Fri Jul 05, 2019 8:57 am
Forum: General
Topic: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF
Replies: 8
Views: 1143

Re: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF

3.2 WIDE BAND PRE-SELECTORS - FIXED BANDPASS FILTERS @ 3.8 MHz It should be evident that all data & calculations shown in the previous Figures 1 to 3 come from an Excel spreadsheet. Unfortunately I can only post pics of Excel, as the Forum software does not allow me to post the Excel file, othe...
by glovisol
Tue Jul 02, 2019 4:17 pm
Forum: General
Topic: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF
Replies: 8
Views: 1143

Re: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF

3.1 WIDE BAND PRE-SELECTORS - FIXED BANDPASS FILTERS @ 3.8 MHz In this post we are going to look at another alternative: build a fixed pre-selector protecting the entire 80 band, 3500 to 3800 KHz. The design procedure is based on the transformation of a Cauer Low Pass prototype into its bandpass eq...
by glovisol
Mon Jul 01, 2019 10:36 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 102
Views: 10984

Re: Receive Antenna & Impedance "Matching"

Looks very interesting...I shall look at it after the holidays! Thanks Phil...

Gianfranco
by glovisol
Mon Jul 01, 2019 8:05 am
Forum: General
Topic: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF
Replies: 8
Views: 1143

Re: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF

2.2. NARROW BAND PRE-SELECTORS - TUNEABLE BANDPASS FILTERS @ 3.8 MHz Using a double gang easily self made variable capacitor, our system Qu rises to 400 or better and the new parameters are as follows: Qu=400 Ql=80 Insertion loss Il=2 dB/single tuned & 2.8 dB/double tuned. Coefficient of coupli...
by glovisol
Mon Jul 01, 2019 7:46 am
Forum: General
Topic: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF
Replies: 8
Views: 1143

Re: BUILDING SELECTIVITY PROTECTION INTO THE RSP FRONT END IN LF/HF

2.1 NARROW BAND PRE-SELECTORS - TUNEABLE BANDPASS FILTERS @ 3.8 MHz In the frequency range 3500 - 3800 KHz, Iron Powder material N2 toroids, have measured ( by me) Qu's of 400 or higher. We must now consider the problem of the tuning capacitor. Using an inductance of 50 uH, easily obtainable with a...
by glovisol
Sat Jun 29, 2019 10:44 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 102
Views: 10984

Re: Receive Antenna & Impedance "Matching"

Yes I still have the external SICSI drives and the Iomega storage chartridges with lots of data & design software, which can be useful from time to time. in the eighties and for all the nineties you had to use MAC for serious work. Windows software was still in toyland, with just about three cra...
by glovisol
Sat Jun 29, 2019 6:05 am
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 102
Views: 10984

Re: Receive Antenna & Impedance "Matching"

Hi Phil, We now have to consider how much strong is "strong" and " and how much "far" is far. If you look here: https://www.sdrplay.com/community/viewtopic.php?f=5&t=3926 you see that for the RSP Processor 2° order and 3° order effects start at a level of -35 /-40 dBm of...
by glovisol
Fri Jun 28, 2019 7:34 pm
Forum: SDR Antennas
Topic: A FOOLPROOF ANTENNA SWITCH
Replies: 25
Views: 7117

Re: A FOOLPROOF ANTENNA SWITCH

Well, now the post by Ian1951 after misteriously disappearing, has re-appered and I can reply. The problem of dry contacts becoming insulated in the long run is caused by oxidation. In relays switching small or negligible currents and exposed to the atmosphere, this used to be a serious problem in t...
by glovisol
Fri Jun 28, 2019 7:21 pm
Forum: SDR Antennas
Topic: Receive Antenna & Impedance "Matching"
Replies: 102
Views: 10984

Re: Receive Antenna & Impedance "Matching"

Hi Phil, The dilemma about selectivity Vs. insertion loss is not really a dilemma, if you carefully consider the data at your disposal. 1) The minimum detectable signal (MDS) of the RSP2 @ 10 MHz (given its rated Noise Figure) can be safely set at -120 dBm. 2) You now have to give a figure to your a...

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