Search found 166 matches

by snn47
Mon Apr 29, 2019 7:54 pm
Forum: Antennas
Topic: Antenna tuning, impedance matching, baluns, common mode currents, my head exploding...
Replies: 7
Views: 2105

Re: Antenna tuning, impedance matching, baluns, common mode currents, my head exploding...

Get a copy of the ARRL or RSGB antenna handbook and you have the Basics in a simple form. If you use a transmission line that has the same impedance as the antenna and is symertical in case of dipoles you don't need any BALUN or UNUN. The same is true for asymetrical antenna designs like ground plan...
by snn47
Mon Apr 29, 2019 7:33 pm
Forum: RTL-SDR Discussion
Topic: confused: spectrum analizer and sdr
Replies: 7
Views: 1475

Re: confused: spectrum analizer and sdr

I am confused if they are your PMSE why would you need to measure the frequencies you operate on? Furthermore I doubt you have sufficient dynamic range with a rtl-sdr stick to measure in presence of much much stronger BC, TV or cell phone equipment. Even a SA like the R&S FSW13 with 512 MHz bandwith...
by snn47
Fri Apr 26, 2019 4:30 pm
Forum: Antennas
Topic: Antenna tuning, impedance matching, baluns, common mode currents, my head exploding...
Replies: 7
Views: 2105

Re: Antenna tuning, impedance matching, baluns, common mode currents, my head exploding...

BAL UN or BAL (anced/ UN (balanced) is needed when you want to connect an unbalanced/asymetrical cable/antenna (e.g.coax) to a balanced/symetrical cable/antenna e.g. a halfwave-dipole. Not mentioned in the name is that BaIun can also provide impedance matching, eg. 1/4 to connect a folded full Lamb...
by snn47
Thu Apr 25, 2019 11:44 am
Forum: Antennas
Topic: Balun
Replies: 2
Views: 962

Re: Balun

BAL(anced/ UN(balanced)is needed when you want to connect an unbalanced coax cable. to a balanced (symetrical) cable or antenna . Some BaIun retain the Impedance some provide transformation eg. 1/4 (Folded Lambda Dipole of ~240 Ohm to a 60 Ohm coax, but often also 50 Ohm to 75 Ohm). A BalaUn is used...
by snn47
Thu Apr 25, 2019 11:25 am
Forum: Antennas
Topic: Another Double Cross Antenna build (went wrong)
Replies: 16
Views: 3626

Re: Another Double Cross Antenna build (went wrong)

Dipoles consist always of 2 radiating elements of equal length. If the lower part would not be needed, it would have been a waste of material right?
by snn47
Wed Apr 24, 2019 11:18 am
Forum: Antennas
Topic: Another Double Cross Antenna build (went wrong)
Replies: 16
Views: 3626

Re: Another Double Cross Antenna build (went wrong)

Can you extend the pole above the dish and increase the distance to the dish. Assuming that your dish is pointing to South (Astra?), it could be the Impact of the dish. It looks like the dish is within/to close to the antenna elements. If you mount the antenna 180° mirrored in azimuth the Problem sh...
by snn47
Sat Apr 20, 2019 3:08 pm
Forum: Antennas
Topic: Another Double Cross Antenna build (went wrong)
Replies: 16
Views: 3626

Re: Another Double Cross Antenna build (went wrong)

ANtenna performance can vary significantly if the dimensions (diameter and lengthof radiator,coax type length) of the reference design are not copied. Also a faulty soldering joint or connection can make the difference betwen works and does not work. Did you use this double cross antenna design http...
by snn47
Sat Mar 30, 2019 5:07 pm
Forum: RTL-SDR Discussion
Topic: is there a way to time-display pulses or alternatively stretch waterfall display
Replies: 1
Views: 537

is there a way to time-display pulses or alternatively stretch waterfall display

I was looking for a way to display e.g. DME, TACAN transponder pulse(pairs). Using SDR# a dash of an DME or TACAN ID, which is about 640 ms long, is only shown as a very thin line in the waterfall diagram. Is there a way to stretch the waterfall resolution to show single DME or ADSB pulses or a way ...
by snn47
Wed Jan 30, 2019 6:13 am
Forum: Signal Identification Help
Topic: RFI? Or something else?
Replies: 3
Views: 13959

Re: RFI? Or something else?

A OTH can also look like the chineese OTH around 7 MHz http://www.arrl.org/news/chinese-over-the-horizon-radar-qrming-low-end-of-40-meters http://www.arrl.org/images/view/News/Chinese%20OTH-R%20on%206999.JPG As the newsletter reported: “A jumping Chinese OTH radar covered the CW DX-edge of our exclu...
by snn47
Tue Jan 29, 2019 8:16 am
Forum: RTL-SDR Discussion
Topic: Long USB-cable vs long antenna-cable?
Replies: 18
Views: 33041

Re: Long USB-cable vs long antenna-cable?

Similar to Coax cable, there are high quality cable and there are cheap low quality cable, though the price of many cable may be high it is not necessarily a way to get a good USB cable. So you might have been just unlucky with the USB cable you bought. You have two (three) reasons for problems: 1. ...