Search found 192 matches

by snn47
Tue May 14, 2019 4:38 pm
Forum: RTL-SDR Discussion
Topic: LNA power supply?
Replies: 6
Views: 1619

Re: LNA power supply?

linear regulated power supply (PS), .... They are less efficient, and run warmer, but generate almost no RF noise. I disagree just having a PS with linear regulator doens't mean that the DC-Output voltage has less noise or spikes (due to lack of isolation between AC Input and DC Output,) compared t...
by snn47
Sat May 04, 2019 10:06 am
Forum: RTL-SDR Discussion
Topic: confused: spectrum analizer and sdr
Replies: 7
Views: 1930

Re: confused: spectrum analizer and sdr

I thought that you should also keep Receiver Intermodulation (Rx-IM) in mind, meaning that not necessarily all signals that you receive may exist in the RF-Envrionment, but can be generated in your receiver. Since I just answered to another post in detail on the effects of Receiver-Intermodulation i...
by snn47
Sat May 04, 2019 9:59 am
Forum: Other SDR Devices
Topic: SDR Upgrade
Replies: 5
Views: 2681

Re: SDR Upgrade

-If i have a strong signal on a frequency, it repeats itself in many other frequencies. -a large amount of spurs in various bands (ie:around 145-160mhz) -plenty of ghost signals in the HF (13-30mhz) All of the above are most likely all from receiver (Rx) Intermodulation (IM). Even if you would spen...
by snn47
Wed May 01, 2019 8:20 am
Forum: Antennas
Topic: RG6 or RG8?
Replies: 6
Views: 2226

Re: RG6 or RG8?

While there a several RG6 type coax on the perfect vision webpage https://www.perfect-vision.com/WebStore/ProductList.aspx?pcid=159&menu=intl I could not find the number you referenced. RG-6 and RG-8 coax differs in addition to the attenuation, which depends on the dielectricum (air, foam, solid mat...
by snn47
Tue Apr 30, 2019 9:09 am
Forum: Antennas
Topic: Another Double Cross Antenna build (went wrong)
Replies: 16
Views: 5244

Re: Another Double Cross Antenna build (went wrong)

Most antenna pattern you find are calculated and are either for free space, meaning idefinetely high above a reflecting surface, or for a given height and a min. diameter of reflecting surface, normally 1/4 Lambda or more. Under any other condition reflections from any surface or object will change ...
by snn47
Tue Apr 30, 2019 8:04 am
Forum: Antennas
Topic: RG6 or RG8?
Replies: 6
Views: 2226

Re: RG6 or RG8?

There are different versions of RG-6 (foam dielectricum) and RG-8 see (solid dielectricum) https://en.wikipedia.org/wiki/Coaxial_cable, which can have mechanical problems or due to heat over time. The difference can be more than 2 dB at 400 MHz for 100 ft, and increase with frequency, but it depends...
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: 3198

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: 1930

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: 3198

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: 1561

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...