Questions tagged [hf]

The frequency range 3-30 MHz. HF radio waves often propagate by bouncing off the ionosphere, allowing communication between continents. This tag may also be used for questions about the 160 meter band (1.8 MHz), which while not HF is often referred to as such due to its similar propagation.

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2
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2answers
30 views

Mounting a hex beam on top of a high urban building

I am moving into a new apartment in the city soon which is on the 24th and last floor of an apartment building. I will have access to the roof of the building also. I'm still trying to understand ...
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1answer
64 views

CMC hurting my SWR. Live with it? Drop the CMC?

I have been using a Par EndFedz Mk2 Trail Friendly 40/20/10 though using the matchbox from an EndFedz EF-QUAD (with Vibroplex’s blessing) so I could transmit at more than 25W. On all three bands I ...
3
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2answers
82 views

Mounting a vertical antenna on a fiberglass mast

I have a multiband SE-X80 HF vertical antenna which works ok from 20 meters to 10 meters with a tuner. It is attached to the railings of my apartment balcony at the moment. This is the antenna : https:...
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3answers
85 views

What's the realistic SSB reception range for 25W on 20m and 40m?

Because of my living situation I am using a Par EndFedz Mk II Trail Friendly antenna with my IC-7300, since it can do 40m and 20m and is only 41 feet long. However, it can only handle 25W. Now, for ...
4
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1answer
51 views

HF SSB etiquette when someone is working quick but not contesting and you're not sure they got you?

When someone is working quickly -- clearly trying to work a lot of stations -- but pretty clearly isn't contesting, what's the etiquette when they 73 you and end the contact but you're not sure they ...
4
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7answers
330 views

QRN: How to chase down a solid S9 noise floor on 40m only

I am new to this, having just set up my station. I have "very bad" QRN on 40m: S9. Here is the setup: High density suburb with flats and houses Yaesu FT450D with fan dipole at 6m-9m above ...
4
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3answers
146 views

RF ground confusion

I'm a bit confused by RF grounding. Let's take a HF 1/4 wave vertical antenna for example. When current flows through the centre of the coax to the antenna, my understanding is that the current then ...
11
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5answers
3k views

Why do operators mention the band when calling CQ on phone?

I'm a new-ish ham, licenced for about one year now. Within that year I've heard a lot of CQ calls from other hams on phone (both HF and VHF), and it seems that a large portion of hams routinely ...
0
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1answer
41 views

Recommendations for Antennas installation with Steep slopes

I have a property that I am trying to figure out the right antenna setup for. Currently running the following Antennas: 1x Hustler 5BTV Vertical with radials 1x Chameleon in a NVIS configuration 1x ...
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2answers
55 views

Does a NVIS antenna have to be exactly below the maximum NVIS frequency to have NVIS characteristics?

For example if the maximum NVIS frequency is 5 MHz in a given region, would a NVIS antenna have to be resonant at less than 5 MHz to have NVIS propagation characteristics or can it be slightly above ...
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2answers
1k views

Dipole versus ungrounded end fed for HF RX

I've built a 2 meter ground plane antenna that works pretty well for RX and has a decent SWR on 2 meters with my Alinco. However, I'm experimenting with SDR quite a bit and would really like to build ...
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2answers
138 views

Choosing a Relay for HF Applications

As part of my 20m transceiver build I'm looking for a relay to by-pass an RF amplifier in the front-end board. So, to be clear, that's after the 20m broad bandpass filter and before the RF mixer (it'...
2
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2answers
531 views

Modelling a "fan dipole" or "fan inverted vee" using EZNEC - unexpected result

I plan to put up a "fan inverted vee" but for various reasons I will not be able to take it down, adjust wire lengths, put it up, test, etc: I will basically have to cut the wires, put it up and leave ...
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1answer
52 views

How to check second-hand ICOM IC-718?

I’m buying a used IC-718 from a local ham. I can verify its function before I decide to buy. I’ve read the manual and know the functions and capabilities. What should I check / look for, apart from ...
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0answers
61 views

Understanding low MUF in VOACAP

I've started playing with VOACAP to better plan and predict conditions on 27 MHz (CB). To my utter astonishment, VOACAP says that I won't be able to communicate on that frequency, regardless of ...
1
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1answer
123 views

Does the price of ham equipment normally rise during winter?

Recently licensed technician here, and going straight into my general class, I'm keeping an eye on cheap (sub-$400) HF radios. I keep reading articles that suggest used radios that normally sell for ...
6
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3answers
2k views

How to stop interference on shortwave radio when connecting to a computer

I have a Tecsun PL-600 and when I can receive clear signals, and they come through just fine on headphones, and through the speaker. If I'm trying to receive RTTY or fax, when I connect the radio to ...
28
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2answers
75k views

Which HF bands are best during the day and which are better at night?

I am rather new to HF operation and have recently purchased my first HF rig. I have read about bands being "open" and "closed" based on various conditions including time of day. As I have been ...
6
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4answers
3k views

Can an HF antenna be put inside a tree?

There are some trees around with branchy tops that seem wider than half of 10M, maybe even half of 20M, and above the nearby rooftops. Can a wire dipole or a vertical be mounted inside a tree? If so,...
4
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2answers
348 views

What is the best time of day to contact Japan from the east coast?

What are the best times in early April to contact Japan on 40M and 20M from Pennsylvania?
2
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2answers
68 views

Hang wire antenna on TV antenna?

I have a TV antenna on the top of my house that I don't use. It is the highest point around so I would like to hang a wire antenna (for HF) on it. Is an inactive antenna going to cause any ...
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2answers
89 views

Tuning wire with SWR LED

I have a QRP rig (Mountain Topper) and a variable capacitor QRP end fed half wave antenna with an SWR LED indicator. The LED doesn't go fully out in all configurations but there is always a local ...
2
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1answer
122 views

Receiving shortwave frequencies from different countries (e.g. North Korea)

This question may be a little strange, but how can I receive radio waves from a country like North Korea (when I live in Poland)? I am interested in this topic, but I don't have that much knowledge. ...
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0answers
29 views

Magnetic and Electric Wall in HFSS

I'm new to RF engineering and I want to ask how to draw magnetic and electric wall in HFSS software? I know magnetic Wall means open circuit in circuit model and electric wall means short circuit, but ...
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3answers
2k views

What is the origin, history behind "Ben's Best Bent Wire"?

Bens Best Bent Wire My uncle, who was a Merchant Marine in WWII used to tell me this. He was a ham, and said it would develop my fist musically. I was a small child at the time, and through his ...
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3answers
311 views

Long range HF polarization

Is it possible to polarize HF signal (20-30m) at long range (thousands of km)? It was commented in my over questions that polarization is not feasible at long range. However in this article is ...
2
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1answer
121 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 ...
3
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1answer
137 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 ...
4
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3answers
373 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 ...
5
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2answers
1k views

RF Bridge Problem - K6BEZ Antenna Analyzer

This question regards erroneous SWR measurements of K6BEZ antenna analyzer (links gone from Internet now) design from 2013 using Arduino and AD9850 DDS modules. There have been many variations of it ...
10
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8answers
7k views

What is the best time of day/Band to make a contact with Hawaii from the East Coast?

I need to get Hawaii for Worked All States, and live on the East Coast (Virginia). Furthermore, I have a poor antenna, and thus only the prime times of the day seem to really be opened for me. What ...
1
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1answer
99 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 ...
29
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6answers
35k views

Can I reduce RFI/noise at the antenna?

Recently, the power was out in my neighborhood for an extended period of time. I fired up my HF rig using battery power and was amazed at the lack of noise across the HF bands. When the power grid ...
7
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2answers
176 views

Why aren't "ghosts" and intersymbol interference due to unmatched impedance (high SWR) a concern for HF receivers?

In amateur radio, we care about impedance matching when we need to keep the load within the equipment's specification (for best performance, or just to avoid damaging a transmitter), when we want to ...
6
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6answers
273 views

If receive performance doesn't depend on SWR, then how can I tune my manual HF antenna tuner by band noise?

The popular question "What is the relationship between SWR and receive performance?" asks if a receiver with a well-matched antenna (low SWR) beats a receiver with a poorly-matched antenna, ...
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1answer
80 views

Need way to indicate when rotary inductor reached its limit switches on a remote homebrew motorized hf tuner

I have a homebrew motorized hf tuner which is controlled by coupling dc from the shack through two BiasTs - one topside, the other in the shack. As I reverse polarity to adjust tuner, will two LEDs, ...
5
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5answers
3k views

EFHW works only on one band - what am I missing?

I tried to build a multiband EFHW antenna as described in articles by PA3HHO, PD7MMA, G0KYA and many others. I decided to start with a short 40/20/(15?)/10 meters version without any loading coils. ...
2
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2answers
317 views

How does end loops on a long wire antenna affect antenna length

I've put up a "random" length long wire antenna for HF in my yard at about 124ish feet about 15' off the ground. I got this length from an online resource. Here's my questions: How does the ...
0
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1answer
61 views

why does time of day affect propagation when talking to the other side of the earth?

i have been told time of day matters for hf propagation. for example, 80m works best at night. but if i qso with someone on the other side of the world, it's daytime. do they just need more power? can ...
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0answers
35 views

HobbyPCB IQ32 SDR Data modes cable?

has anyone DIY datamodes cable for HobbyPCB IQ32 SDR ? Im thinking of using SPKR/MIC/PTT port and expose it either towards external USB soundcard (or USB soundcard stick), or directly to laptop USB. ...
4
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2answers
352 views

Recommendations for starting out with HF for an amateur

I'm a beginner who's nearly half a year from receiving my ham license in India. I want to start with HF radio and wish to build my own rig. Currently I have looked and multiple designs using the ...
1
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1answer
73 views

Sunspot numbers? forecast? broadcast on CW/HF

I have vague memories from the early 1990:s of some sort of service that broadcast something related to sunspot numbers, in CW, probably shortwave. I think the world "BOULDER" was in there ...
6
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2answers
108 views

Where to find HF channel models or statistics?

When designing a waveform for packet radio usage, it'd be helpful to know a few things, mainly distribution of coherency bandwidths distribution of coherency times Whilst such statistics are ...
0
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2answers
150 views

How do you know if you're on a 10 meter band?

I am just getting into ham radio, and I find it very interesting, but to make phone calls, you have to be on a 10 meter band. Does anyone know how to infer the band you're on is 10 meter? Thank you ...
2
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2answers
358 views

Broadcast signal deviating with time

I've been just scanning through the HF band at night seeing what all I can pick up, and I'm trying to figure out a particular signal. I'm using a VHF discone, which isn't ideal, but it works well ...
4
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3answers
670 views

What are the technical reasons that there are no FM transmissions on the long, medium, or shortwave?

Why are there no frequency modulated broadcasts on the long/medium/short wave, but only on VHF? I'm sure there are many historical and political reasons (long/medium/short wave were already in use for ...
2
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2answers
134 views

Would Orbital Angular Momentum (OAM) multiplexing work over HF bands?

OAM (Orbital Angular Momentum) Multiplexing is a form of multiplexing capable of high data speeds on limited bandwidth using the physical properties of EM waves. An experiment in 2012 transmitted two ...
4
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2answers
113 views

I just can't get out on my car mounted HF

Would love some advice from you seasoned vets. I have an FT857D in my car which I tend to only use (and really want to use) when I'm stopped and setup camping. I bought a portable Windom antenna which ...
3
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4answers
790 views

What is the use of dual VFOs?

What is the value of more than one VFO in an HF transceiver? Many novice rigs only have a single crystal oscillator, and a vast number of famous classic transceivers, HF kits, and QRP rigs only have a ...
0
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2answers
221 views

Why does the HamQSL website say the 40m band is fair and the 20m band is poor during the day?

http://www.hamqsl.com/solar.html Why is 40m shown as "fair" while 20m is "poor" during the day. Shouldn't 7 MHz be getting absorbed by the D-layer more than 14 MHz?