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12 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&...
2
votes
0answers
34 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 ...
0
votes
1answer
22 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 ...
1
vote
0answers
47 views

have an unwanted radio tower

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
3answers
43 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
43 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
59 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 ...
-2
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0answers
35 views

I am trying to use dmr via internet what speed is required [closed]

I am using blue dv thumddongle and brandmister systeam
4
votes
1answer
136 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
52 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
0answers
30 views

how are frequncies,band widths, speeds,channels are allocated for catv company from provider to House? [closed]

for a cable company that delivers internet,TV how could be frequncies,band widths, speeds,channels be distributed, like how many Mbps come from internet provider,how many channels ? how many channels ...
0
votes
1answer
45 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
62 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
23 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 ...
4
votes
7answers
277 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
23 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
46 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
83 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
20 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 ...
3
votes
1answer
59 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
50 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
87 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
29 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
19 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
94 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
189 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
21 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
129 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
69 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
24 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
87 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 ...
0
votes
1answer
14 views

Connecting Mobilinkd TNC2 to Mac for Xastir

I am not sure what to put in the TNC Port window on Xastir if I'm using a Mobilinkd TNC2. Xastir has directions for just this however, it is for Ubuntu Linux. https://xastir.org/index.php/HowTo:...
2
votes
1answer
61 views

Reducing cross-band noise from plasma TV

I have a noise problem on 40, 20, and 15 meters originating from the plasma TV I own. Turning on the TV raises the noise level by 2–4 S units, depending on the frequency. The TV is located below the ...
3
votes
1answer
57 views

How do I write a modem for DireWolf?

I was looking at the selection of modem bauds for DireWolf and it seems the highest baud modem is 9600 baud, and I am using a sound card that can reach 48 khz. Is there any way that I can write a ...
2
votes
2answers
90 views

Coupling 2 Antennas to one line?

Imagine two dipole (or Yagi) antennas as might be used to create a circularly polarized combination antenna. The two are physically oriented (rotated) by 90 deg, and if in the same receiving plane, ...
5
votes
1answer
62 views

can the adhesive used in thru-glass antenna couplers be replaced?

I recently bought a pair of self-adhesive thru-glass antenna couplers for my mobile radios and erred in mounting both of them, which required me to peel them off the side window glass in my minivan. ...
0
votes
0answers
38 views

Charly 25 vs mid/top-end SDR transcievers [closed]

I am interested in independent theoretical performance feedback for Charly 25 SDR (based on RedPitaya 122-16 board) compared to more conventional SDR transceivers like ICOM 7610: Reference clock ...
3
votes
2answers
146 views

Dual Polarization Yagi Antenna for 10 m

Imagine that someone has built a 4 element horizontal yagi antenna for 28 MHz with elements insulated from the boom, and with the driven element not split in the middle and using a gamma match to set ...
1
vote
2answers
67 views

Yaesu FT-70DR Earpiece

I recently purchased a Yaesu FT-70DR and would like to use an earphone of some sort just to listen. On Yaesu's site, there seem to be only 2 official options: SSM-57A Earbud speaker mic with PTT (...
8
votes
2answers
607 views

What is the appropriate length of an antenna for a handheld on 2 meters?

I want to upgrade the stock antenna on my Baofeng uv-5r for which I mostly use the 2 meter band. The quarter wavelength for this band is about 19.2 inches, but when I look for antennas, they are ...
3
votes
0answers
48 views

Any tool for finding satellite passes that overlap *two* given locations?

gpredict is nice. Well, it's OK, to find the next passes for a set of satellites with sufficient elevation for one location. What I want is something where I can put in two coordinates, and get out ...
0
votes
0answers
28 views

USA made handheld [duplicate]

I am looking for advice on new to HAM studies. I have a pair of FRS Motorola T800 walkie talkies and an old pair of REalistic TRC-215 6 channel, 5W, CB handhelds. As I read, and ask questions, a ...
4
votes
1answer
88 views

Debugging SM0VPO's spiral loop antenna build

I had built SM0VPO's spiral loop antenna. And here it is. Recently I got myself a NanoVNA to see how finnicky it is to be tuned with that poor man's tuning cap. I brought it from 12 MHz into the 14 ...
2
votes
0answers
44 views

Biconical antennas - bandwidth and installation

I am posting this question (and its related question) here because of the unique expertise that Ham Radio Operators have as it relates to antennas. I'm a newish Ham and really appreciate your help ...
1
vote
2answers
99 views

Trying to identify and understand this antenna design - ground independent dual band vertical

This is the insides of a common dual band antenna 2m/70cm, made by diamond or nagoya. its generally labelled as: 1/2 wave radialless (144MHz), 2 x 5/8 wave radialless (430MHz) Its meant to be ground ...
2
votes
3answers
87 views

Constructing a ground level antenna array to monitor radio frequencies using SDR

New to this community and also a newish Ham. Hello everyone. This question could easily have been posted under 'Astronomy', but I thought I would start here since Hams tend to be quite knowledgeable ...
3
votes
3answers
248 views

Is The Lowest Antenna Terminal Feedpoint SWR Always Optimal?

Intuition might lead one to believe that the antenna configuration with the lowest SWR(50) across its input terminals would provide the best radiation efficiency for the antenna system. But is that ...
2
votes
1answer
24 views

alinco dr-635T receive squelch will not open in DCS mode

Newbie here with a question: I have programmed my Alinco DR-635T for use with a variety of local repeaters. Half of these are opened with CTCSS codes and the rest with DCS codes. When monitoring any ...
5
votes
2answers
121 views

Can an oscilloscope be used as an RF voltmeter?

I just recently acquired a slightly functional Icom IC-735 HF radio, and am trying to resurrect it. The service manual outlines procedures that specify the use of an RF Voltmeter, which I do not own. ...
4
votes
3answers
70 views

High-Z RF amplifier for magloop RX vs Q-factor

I've noticed that increasing load on magloop reduces it's Q-factor, it becomes less selective. Traditional way to approach this is reducing size of pickup loop, or alternatively, using transformer. ...

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