Questions tagged [vhf]

Very High Frequency is the frequency range 30-300 MHz.

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1answer
463 views

Gain in long wire antennas

DARA (you know, Hamvention) TNG is looking for projects. Thursday, I will be proposing building and characterizing a vertically-polarized 1 wavelength on a side reentrant rhombic. Since in doing the ...
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3answers
393 views

Weird Harmonic Issue on Raspberry PI FM Transmitter

So I talked to my neighbor about my Raspberry PI, harmonics and his emergency radio. He told me to fire it up, as we saw the FCC sticker on it, meaning it is in compliance with Part 15. I started my ...
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3answers
3k views

Antenna for a cramped attic

Brand new Ham. I bought a cheapo UV5 right before I got my call sign. I want to set up a decent 2m/70cm station for starters and I realize that a better radio is important but wanted to knock out the ...
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7answers
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Is a ground plane necessary for transmitting and receiving with a vertical (monopole) antenna?

I've read the post here: https://electronics.stackexchange.com/questions/77256/why-do-some-radio-antennas-require-a-path-to-ground-and-some-do-not which says The antenna system requires a "ground ...
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1answer
131 views

What were the reasons why ATIS identification was introduced?

I am just about to make my inland waterways’ marine VHF radio license in Germany. In Germany, all inland marine VHF radios must be equipped with an ATIS transmitter, which basically sends the stations’...
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4answers
2k views

Why can't VHF / UHF be used with ionosphere reflection?

HF radio can be reflected by the ionosphere, giving very long range communications. Why can't VHF / UHF used with ionosphere reflection? Is it due to the attenuation of the atmosphere over that ...
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3answers
549 views

Why is VHF better than UHF in this situation?

One of the sample questions for the British foundation level test is: An amateur has the choice of VHF or UHF for a particular contact of some 25km. Which statement below best describes his choice? ...
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2answers
759 views

Is my low-power VHF transmitter dangerous?

I use a Raspberry Pi for transmitting FM on 107.9 Mhz. It uses square waves and has a power of approx 0.085 Watts, but just to be safe: If I have a 1 watt transmitter approximately 1 metre away from ...
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3answers
2k views

Feeding a dual-band UHF and VHF Yagi antenna

I just built a UHF Yagi antenna for my HT, and I was thinking about adding VHF elements. If I do, could I just connect the coax directly to both sets of elements without a diplexer?
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1answer
103 views

Power handling of a simple VHF ground plane

The ARRL welcome pamphlet contains instructions on building a simple ground plane antenna and specifically comments on its use by handy-talkies. However, I wonder what the actual capability of this ...
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1answer
490 views

2m loop with sense antenna for DF

I would like to construct a 2m Loop with a sense antenna. I have built just a loop antenna with great success that is resonant at 2m finding null's works quite well on local repeater outputs. I would ...
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2answers
225 views

Amplified antenna & typical boombox radio

Can an amplified antenna be connected to a typical boombox radio with a telescoping antenna without damaging the radio?
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1answer
148 views

Transverter common versus split-if connections

I have a radio (Flex-1500) that has low level transverter outputs. They can be configured as either a common or split-if. I also have a DEMI transverter that can easily be wired up for common or ...
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1answer
90 views

Help with small dish antenna on 2m/440

I have an oblong dish network antenna that I want to convert to 2m/440 usage. I have seen the one for the 14 foot dish but I do not have one. Not sure if I should wind a coil and mount it in the ...
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2answers
110 views

Filtering VHF FM on my DTV signal

I've noticed that when I transmit on my HT when I'm watching TV (OTA), the signal drops and the screen goes blank (or digital "static") and then returns when I stop. I've replicated the issue by ...
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2answers
132 views

Any ideas as to what I might be picking up on SDR?

Any ideas as to what I might be picking up on SDR? They make for some strange patterns. Picked them up at the following coordinates: (31.514596, 74.345092) using GQRX, tuned to 217.25 MHz. As for the ...
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1answer
651 views

What is pinout for headphone FM radio antenna?

My Android phone (as many others) have FM radio receiver on-board. But apparently, it has no internal VHF antenna at all, since there is no signal at all w/o headphones plugged in and sound quality ...
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1answer
234 views

Looking for documentation on Kenwood NX-700 AFO and DEO Signals

I'm studying the accessory connector (DB-25) from a Kenwood NX-700 radio. It seems that I might use the AFO and/or DEO signals, but I haven't been able to get proper documentation on such pins/signals....
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2answers
4k views

Tuning/trimming a ground plane antenna

I've built a ground plane antenna with a 19.5" vertical and 4 20" radials. Currently, at 147.135 MHz my SWR is 3:1, clearly not ideal (and even bad for the transmitter!). I'm reluctant to start ...
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1answer
720 views

What material is best to design a dipole antenna working at VHF frequency? [duplicate]

I need to design an antenna using the tool FEKO. The antenna is supposed to work in VHF frequency and has a gain of around 2.2 dB. What is the best material to use and what are the specifications of ...
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4answers
2k views

Good Hidden Antenna For 2m

I would like to have an antenna outside for 2 meter VHF use but I do not want it to be expensive and I won't be allowed to put it up if it stands out too much. Does anyone know a good antenna to buy ...
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2answers
150 views

V/U Packet Rate Limits

I'm studying for the General exam and I've encountered some questions about maximum baud rates on various bands. They seem... extremely optimistic. Given the trouble I've had investigating 9600 baud ...
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2answers
1k views

Are chokes necessary for VHF and higher frequencies?

I am trying to install a VHF/UHF antenna on my truck, and I have been studying everything I need to do that. I keep reading about chokes, in particular here: http://www.k0bg.com/choke.html However, ...
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2answers
2k views

Which Frequency Band(VHF/UHF) is most useful for satellite in MEO?

I want to get to know about the satellite communication at 8000-10000 km, During that, I come across the VHF and UHF. In that I am facing problem for deciding the frequency band for communicating with ...
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3answers
446 views

High SWR on a Jeep with Spare Tire Mount

I just installed a spare-tire mount and Browning BR-180 dual band antenna on my Jeep JK. Initial SWR testing show nothing higher than 1.4:1 across both bands so I didn't try to tweak it. Then I put ...
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3answers
9k views

Where are the baluns for VHF and higher? How can one be made?

In another question, commenters recommended that I look into adding a 1:1 balun to a dual-band dipole to eliminate the feedline as a radiator. As I understand it, a 1:1 balun also functions as a choke,...
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2answers
1k views

Moon->Earth 433MHz link achievable digital bandwidth

Let's assume we have the following situation: Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz. Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
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4answers
15k views

2m or 70cm FM mobile radio for digital mode operation

Are there any 2m and/or 440cm FM mobile radios that have audio inputs for supporting digital modes, like PSK31 or SSTV? I have a Rigblaster that I use with my HF radio so I could get a mike cable and ...
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2answers
70 views

Extracting received power info from teletype like audio

Is it possible to digitally extract received power info (like VU meter perhaps) from and PSK31 audio (or alike), actually the mode for text encoding over audio hasn't been chosen yet and the ...
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1answer
153 views

Radio Modem suggestion [closed]

I need to transmit digital data, from an Arduino, Raspberry or alike, but using VHF band (aprox 150 MHz), would anyone care to suggest a cost effective device to use as transceiver? 10W would be ...
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1answer
152 views

Using 'amodem' to transfer digitally using a UV5R

I reviewed docs for amodem, and it looks like I can send files and possibly other things with this. I should only need to prep my computer as per the doc and set VOX correctly. Does anyone have ...
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2answers
8k views

Looking for a UHF / VHF transceiver for PC.`

I am looking for a simple UHF / VHF transceiver that I can plug into my PC via USB and be able to RX/TX on one channel, using the built in mic... Maybe even record the RX from the freq. Everything I ...
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1answer
4k views

Programming VHF To CB

New to this particular site on StackExchange and new to amateur radio period so bear with me: I'm looking into buying a VHF radio for work related purposes. More specifically the Icom IC-2300H. I've ...
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1answer
64 views

VTS messages vs AIS

When arriving in a port, complementary to her AIS signal (encoded VHF message) it seems that the vessel also has to emit a voice message on a predifined VHF frequency to identify herself as part of ...
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1answer
187 views

What is the best way to get propagation VHF map for FM repeater?

Is there a way to get a professional propagation map for my VHF 50 watt repeater?
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2answers
4k views

Is there an optimum Antenna Feedline Length for mobile installations?

I bought a ham radio antenna mounting kit for my car that includes ~16' of coax. One end has a trunk lip NMO antenna mount, the other end has a re-solderable PL-259. I asked the sales person if it is ...
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3answers
3k views

Good FM receiver single-chip IC for simple VHF receiver?

Is there an IC out there that implements all, or most all, of a simple FM receiver in the VHF range? I'm interested in doing some experiments with using DTMF over the air for tele-commands and the ...
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1answer
237 views

Using RF6886 Power Amplifier for VHF design

I want to use RF 6886 power amplifier for VHF band design. The datasheet doesn't mention VHF design specifications. Has anyone used the PA for VHF design? If yes then please share your designs.
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2answers
156 views

What type 2 m /70 cm antenna to use when I want to receive a number of spacially separated beams?

So I have a 1.5 m by 1.5 m window. Through it, I have a number of spatially separated ~10 cm wide "beams" coming from local repeaters. It looks something like this: Outside of the marked areas, ...
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1answer
151 views

UHF Into VHF Power Amplifier

What would be the result of accidentally applying a UHF signal to a VHF power amplifier? Say a 70cm transmission from a dual-band 2 meter / 70 cm radio into a 2 meter PA, assuming the input power is ...
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5answers
777 views

What would be the easiest and most cost effective ground system for a startup UHF/VHF station

I just passed both my Technician and General Class license this past weekend, and am now contemplating my first station. To get my feet wet I'm planning on getting a Yaesu FT-7900R Dual band Radio ...
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3answers
1k views

Improving VHF airband reception

I'm trying to receive VHF airband transmitted from a nearby airport via RTLSDR and having a hard time doing so. Obviously the stock antenna is useless in this situation. I tried building a quarter-...
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1answer
124 views

Pseudorange in VHF band navigation and precision phase tracking

I am thinking on what is the practical limit of precision for VHF positioning system (like currently obsolete and gone "Transit" system). It is well known how GPS receivers calculates pseudorange to ...
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1answer
1k views

Balun and impedance matching suggestions for dipole antenna

I'm a newbie who is attempting to build a half-wave dipole antenna that will be located in the rudder of a sailplane. 123.3 MHz is the most important frequency to me, although it's reasonable to ...
6
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1answer
606 views

FM radio in car gets interference from APRS beacon

The FM broadcast radio, factory installed in my car and usually tuned to 88.6 MHz, gets some interference from the 5W APRS transmitter on 144.800 MHz. It sounds like if the sensitivity of the ...
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2answers
389 views
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2answers
444 views

2 meter dipole of work vehicle

I am about to purchase a Baofeng HT. I have one I am thinking of using primarily in work truck. I can't really drill holes or have antenna be too obvious. On Amazon I found a 2 meter 70cm 2m dipole....
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2answers
542 views

Airband VHF antenna challenge

I have a very difficult antenna design/installation challenge. I need to install an VHF antenna (118 to 140 MHz) into a nearly all carbon fiber glider. The radio provides 5 watts and 50 ohm, and most ...
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1answer
94 views

Antenna for 6M, or Antenna system?

Here, in VU-land, 6M allocation is from 50 MHz through 54 MHz... which is a fair chunk of spectrum. If I think about a half-dipole antenna; between 50/54 MHz it's length varies by over a foot ... and ...
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1answer
755 views

VHF / UHF - Terrestrial Circular Polarized Antenna

I've been doing mostly HF for the last 20 years and just recently installed a 2m/70cm mobile rig in my shack for base station work. I like to work FM simplex and repeaters when the HF bands are not ...