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votes
1answer
44 views

How to get the “real” number of samples coming in an sdr

so I am fairly new to this SDR and dsp thing, I am working on a project that calculates the ppm and adjusts the offset, now I kinda got the idea of how to calculate the ppm after going through the ...
3
votes
2answers
71 views

Saving snapshot of NanoVNA (v2) data for later review, analysis, comparison, etc

I have a NanoVNA (v2), and I'm using it with vna-qt. I want to capture the raw data from a sweep for posterity, so that I can someday compare different antenna variants for things like SWR, resonance, ...
2
votes
2answers
72 views

antenna element with “doubled up” nested aluminum rods for added stiffness

I'm building a full-size quarter-wave 20m vertical antenna (approx. 18 feet long, plus a trio of Hustler mobile resonators at the top to add 30, 40, and 80 meters). To make the top 12-14 feet stiff ...
5
votes
1answer
223 views

Failing to detect Hydrogen line with 105cm dish

I've seen many examples of roughly 1 metre sized dishes being used w H+ sawbird and an SDR to detect and analyze Hydrogen line signal, and have been trying myself but can't seem to get anything beyond ...
2
votes
3answers
74 views

Where can I find the official rules for Amateur Radio usage in Sweden

A number of years ago I was very much into Ham Radio in Canada. I have now moved to Sweden and am thinking about getting back into it again. I can not find any clear set of rules as to how Sweden ...
3
votes
5answers
722 views

Can I learn cw at too high wpm? Should I slow it down?

I've been learning to decode cw for a while now, mainly by using the Word training feature of https://lcwo.net . I use this rather than the exercises with random characters, both because it's more fun ...
0
votes
3answers
74 views

change LC parameter digitally

LC circuit is the main element of every frequency generator, I intend to make an FM transmitter, but many opensource circuit use analog variable L or C part to set and adjust the target frequency My ...
2
votes
0answers
57 views

MFJ-939 not working with FT-450 - TUNE blinking

I have recently bought second hand MFJ-939Y for FT-450/950. I have Yaesu FT-450 (plain, without D or AT). Since the tuner did not come with a cable, I have built my own. (I am 33yo IT engineer with ...
0
votes
2answers
47 views

Not able to understand some operations in rtlsdr library in python

Here is the part of the program I am having problems with: samples = sdr.read_samples(16*1024) power, _ = mlab.psd(samples, NFFT=1024, Fs=sdr.sample_rate /1e6) ...
3
votes
1answer
56 views

Where exactly does atmospheric noise (QRN) come from?

Where does the noise I can hear on my 28 MHz receiver come from? I'm not talking about the inherent noise produced by the internal circuitry of the radio, I mean the noise received by the antenna. It'...
3
votes
1answer
90 views

power supply / LiFePo4 battery backup compatibility

I want to create a battery backup for my radios. Initially I'm thinking of using an Epic PWRgate and a LiFePo4 battery, so the battery is charged by the same power supply that's running the radios. ...
4
votes
2answers
629 views

What are the EXACT rules about FCC vanity call sign assignments?

I'm a US extra class, but a little late to the party, so to get a short 1x2 I have to fight it out at the vanity call sign fair. I thought I understood the rules, but apparently I don't. The only ...
4
votes
2answers
296 views

Problem with sample rate

So I am working on a project that involves me to check real time difference between samples.I am fairly new to this so after a bit of researching I wrote a simple python script for it, here is the ...
0
votes
1answer
37 views

GNU Radio transmission for a set amount of time

I am trying to transmit a signal in gnu radio and after a set amount of time have the transmission cut off. For simple example, I have a sine wave that I want to transmit for 30 seconds then after ...
3
votes
1answer
108 views

Troubleshoot ICOM IC-745 intermittently shows no power on transmit

I have an old IC-745 I bought used last year. Recently it seems to be malfunctioning intermittently. It is receiving well on all bands as far as I can tell. Sometimes when transmitting, there is no RF ...
3
votes
1answer
94 views

Using crocodile clips to make modular QRP antennas? Are there downsides?

I'm trying to get into backpacking QRP, which has lead me to read up on various ways to construct very portable wire antennas. I would ideally like to have a single antenna for the CW parts of the 40, ...
2
votes
1answer
65 views

Why does QPSK signal in GNU Radio shift away from my center frequency at higher frequencies?

I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
1
vote
2answers
101 views

Do VNA (nano) suffer the same effect of coax length to swr, as swr meters do?

A SWR meter will vary in swr with coax length if unbalanced as your coax length is around 1/2 wave length multiple. Does a VNA ( nanoVna ) in this case experience the same effect, (obviously assuming ...
0
votes
0answers
71 views

Writing “Wav” file in GNU Radio 3.9.0

I need to burn an audio file received from a computer sound card. But in the new version of the gnu radio, I found that the "Wav File Sink" and "Wav File Source" blocks were gone. ...
4
votes
3answers
312 views

Is testing SWR *practically* less important for 2m/70cm than HF bands?

Totally new amateur operator and I've noticed that a lot of material e.g. Your Tube videos, blogs, forums when discussing metering VSWR mainkly seem to be talking about HF bands. I also see fewer VSWR ...
1
vote
1answer
79 views

There are good guides for building 1:1 current baluns. What about 4:1?

Some dedicated hams have spent a lot of effort gathering empirical data on various constructions for common-mode chokes. For example, G3TXQ's work is commonly referenced, and K9YC's is pretty well-...
0
votes
2answers
116 views

1/8 wave 3-element 2m beam antenna

Here's what I am working on, and someone please tell me if I'm doing this right or wrong, but be kind and gentle. Center frequency 146.520MHz Driven element is 1/8 wave 10.25" long set at 6.125&...
6
votes
3answers
153 views

Antenna options

I am considering a new ham station in a relatively urban environment on the South coast of England, and would like like some ideas / feedback on antenna options. Aim is to get reasonable performance ...
1
vote
1answer
167 views

Implementing a BPSK and 4-FSK transmitters in GnuRadio (GRC) with USRP?

Currently trying to transmit a BPSK and a 4-FSK(MFSK) signal via GRC using USRP, I have two attempts at it but don't seem to be going anywhere. Still fairly new to GRC. For the BPSK, how will this ...
3
votes
0answers
102 views

have an unwanted radio tower [closed]

I have a 190 foot tall am/fm radio tower I need to take down. Taking it down with big enough crane and manlifts and a torque crew will be quite expensive. It is a guyed lattice tower that if ...
0
votes
2answers
86 views

How do I set the RX frequency on a R820T/ R820T2 based SDR

My question relates to the specific programming of an R820T/ R820T2 based SDR for a specific frequency. I'm trying to build a self contained and auto initializing Raspberry Pi 4-based (ignore that ...
3
votes
1answer
75 views

How do I sign up for LotW as a new ham?

I installed tqsl to get started with LotW, but the first screen requires me to enter "Date of the first QSO you made or will make using this callsign". I ...
1
vote
2answers
138 views

Using a parabolic dish for working the 70cm band - Am I missing something?

I have read a lot of times in this forum that C-Band TV dishes are not suitable for operating 70cm. However: Suppose that we have a 2,4m dish. By assuming a global efficiency of a 60%, our total gain ...
5
votes
1answer
254 views

What is a 'Call' Channel?

While programming my Icom radio it has MR (memory)channels, VFO (Variable Freq) channels and Call Channels. What are call channels as comparred to memory or vfo channels? What is their use?
1
vote
1answer
76 views

Antenna Tuner Range

I have a Kenwood TS-480S and a Kenwood TS-870S both with built in antenna tuners. On the TS-870S I have a ZS6BKW multiband antenna and on the TS-480S I have a vertical whip with two counterpoise lines ...
0
votes
1answer
52 views

Estimating SWR based on multiples of resonant length

I am planning to buy a Xiegu G90. It has an internal tuner that can tune up to SWR 5:1. Does anyone know if I have a resonant antenna on 40m, what I will have for a SWR on 80m?
0
votes
1answer
68 views

Circuit for RF Splitter [closed]

Does anyone know of any resources which describe how to design a circuit with one RF input and multiple (at least 6) RF outputs, whereby the signal strength of each output matches (does not exceed and ...
0
votes
1answer
26 views

4NEC2 shortening factor “x”

I read on pg5 of Antenna Simulation with 4NEC2 about shortening factor "x". It is very specific and I can't figure out how to use it in a general nec file. It sounds like SY x=0.907 in the ...
6
votes
7answers
400 views

How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...
1
vote
1answer
28 views

How to model a curved element in 4NEC2

I am in kindergarten with 4NEC2 and trying to model a Gray-Hoverman TV antenna. I have someone else's model and understand most of the file parameters. I have added VHF elements that have S curves at ...
2
votes
0answers
79 views

Installing GNU radio on android

I want to install this miracle program on my smartphone in order to get more mobility. I found such a solution exists: https://github.com/bastibl/gnuradio-android However, I could not do everything as ...
3
votes
3answers
99 views

If a sealed, non-airtight pipe is used as antenna element, how big of a problem is condensate trapped inside?

I'm building a vertical antenna. The lowest portion of its element consists of 3/4" type M copper pipe, with end caps that will be soldered on and 3/8-24 screws poking through at both ends (so ...
1
vote
0answers
23 views

#APRS error ? (only visible on aprsc status)

I'm playing with Nodered that I'm trying to use to place an aprs object: it works but it does not suit me! No error on findu.com, correct display of frames on aprs.fi or on aprsdirect.com ... but on ...
4
votes
1answer
92 views

Does the FCC e-mail when a vanity call sign is approved?

I submitted an application for a vanity call sign a little over 18 days ago, and it's marked "pending". I presume that it will be processed soon, but the FCC's ULS search page is being slow ...
1
vote
1answer
77 views

Lowest noise MMIC for HF? (160-20M)

I recently learned that these fancy modern ultra-low noise MMIC, while having <1dB noise figure around 1Ghz could be quite bad at low frequencies due to 1/f noise. What is lowest noise MMIC then ...
2
votes
3answers
116 views

How is the Hackrf able to achieve 20MHz of bandwidth with an ADC that only allows 22Msps?

The way I understand it, is that to avoid aliasing on an ADC, you have to be in the first Nyquist zone (so half the sampling speed). What doesn't make sense to me is how the Hackrf is able to bypass ...
0
votes
1answer
32 views

Software to model autotransformer matched end fed dual band, 4nec2?

I have several ground independent dual band antenna of different makes, but they all have the same type of matching circuit to make them ground independent / radial-less and match say 5/8 elements, ...
0
votes
0answers
25 views

Setting the maximum Tx Power value for the USRP transmitter

In order to simulate the measurements on the computer (in the WinProp environment) I have to set the maximum Tx power: To find out what the transmitter signal power is, I checked it on the spectrum ...
4
votes
1answer
100 views

Frequency selective surfaces working principle

I've seen that sometimes frequency selective surfaces are used to load a certain impedance to a certain antenna (for instance for input matching purposes). These surfaces act like a filter on the ...
4
votes
2answers
230 views

What do you call antenna that combines multiple Hustler resonators (using a VP-1) above a shared mast?

I know that a Hustler MO-3 54" mast with something like a RM-20S resonator on top is officially an example of a center-loaded quarter-wave vertical... ... but Hustler also allows you to mount ...
0
votes
0answers
36 views

Viewing SSTV with QSSTV/GQRX

I have an IQ file and have the following information: 7.171Mhz / 2.5 megasamples per second My question is with this information, can I view view from the IQ file ...
1
vote
2answers
148 views

How many cars/devices can connect to a transmission from a 7 Watt FM transmitter

I currently own a 7 Watt Frequency Modulation (FM) transmitter that I purchased from eBay some years ago. We are planning a drive-in cinema setup where the transmitter will be placed 5 meters above ...
2
votes
1answer
111 views

Why is QRN so bad on the low HF and MF bands?

If one tunes an HF/MF radio at night, the lower the frequency (or the longer the wavelength) of the band, the more QRN (static and atmospheric noise) there is. 80m is noisier than 40m, and 160m is ...
0
votes
0answers
53 views

Can I use a DireWolf based digipeater to work the ISS digipeater?

I've recently become interested in ham radio, particularly AX.25/FX.25 packet radio. I ordered the basic setup (RPI, DireWolf, BaoFeng, a sound card, and some cables) and I was wondering with this ...
2
votes
2answers
101 views

Selecting antenna for rocket telemetry system

I'm currently in a rocket team and we are building a rocket that can reach 3000m (10.000 feet). I am responsible to find an antenna for the telemetry system. I was searching on the net to find the ...

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