Category Archives: Antennas

The SDRPlay RSP1A-a momentary lapse

At the RSGB Convention last week I broke my pledge to have a 100% homebrew station. There was a demonstration of an SDRPlay RSP1A right next to the Martin Lynch stand with a small pile of boxes on sale! Not only is it a wide band receiver there is also spectrum analyser software available and all this for just less than £90.

The justification was simple; I build transmitters and need to be able to check the harmonics and other spurious signals to conform to licence regulations. It does not have to be an absolute measurement just the level of the spurious emissions compared to the carrier. And spectrum analysers are expensive.

Then there is the imminent launch of Es’hail, so I need a 10Ghz receiver to listen to it. The conscience clincher was a demo by the microwave group of a modern satellite TV LNA connected to an SDR receiver. Simple. Another reason to get the RSP1A.

And then there is 630m. You get the message, justification for the temptation and I must confess I had a moment of weakness and succumbed. I am trying to atone by finishing the remote tuner.

Not had much time to play but what I have seen is impressive. SDR receivers are incredible, amazing etc. This morning I listened at the top end of 80m for the transatlantic DX spot, 3.798Mhz and was astonished to hear AA8KB at 5-7 on the meter. This is on an untuned inverted L sloper with the high end at about 10m and low end at 6m.

This is a short recording of AA8KB holding the recorder close the the PC speaker.

I can only confess to this lapse and argue that this was a one-off purchase of an extremely useful piece of kit!

The usual disclaimer, no connection with the company and these are my own views.

Update a half hour later. Just gone back to the SDRPlay and found the RF gain was almost turned to minimum.

Topband 160m links and info

Here are some links to Topband, 160M, web sites in no particular order nor offering any sort of endorsement or recommendation. I am sure there are many more but for the newcomer they offer an insight into what the band is about.

I am about to order some relatively simple gear for 160M in the form of AM receiver and transmitter kits. More to follow.

The RAT5 RX and FAT5 TX kits
Simple but effective, AM,  RX and TX projects for 160m

160 Meter Radio Propagation Prediction Table
The table above represents a rough approximation of radio propagation conditions on 160 meters (affectionately known as Topband). It is to be used as a guide only and is not a definitive forecast. It is based upon selected high-latitude magnetic observatory data which is used to estimate the influence of the auroral oval on 160 meter path propagation (refer to the March and April 1998 issues of CQ Magazine for details: “160 Meters: An Enigma Shrouded in Mystery”, by Cary Oler and Ted Cohen).

The fabulous G4FPH topband WebSDR
Welcome to this WebSDR receiver (running PA3FWM dist11 software – big thanks to Pieter-Tjerk), located near Stafford in central England (IO92AS).

160mt
160 metres being a band like 6 metres offers challenges just above the AM broadcast band is not the easiest band to work DX, operating portable or mobile ETC.
Some AM portable radios can be adjusted to receive 160 metres by adjusting the local oscillator, Car radios can be also adjusted up but they can be very difficult and would suggest using an old unit with AM only.

160m am radio conversion
If you don’t have a general coverage receiver you can convert an ordinary am wireless. As most
broadcast sets cover up to about 1630khz it is possible in most cases to tweak them up to above 1.8mhz.

ONE SIXTY METER CROSSBAND RADIO
Stay tuned to this spot for the latest information on the regular one sixty meter crossband transmissions from vk3ase. Listen from 2230hrs Saturday evening till 0200hrs Sunday morning.  And Wednesday night/Thurs morning (Australian eastern time)on the one sixty, eighty and two meter bands for the largest  amount of bilge imaginable. The content of these missions range from discussions about radio, audio, computing and other related subjects through to social techno babble. Actually most of it is very silly and serves to modulate the carrier to comply with regulations. The program material is drawn from the extensive crossband archive going back 40 years and live missions.

Getting on 160 Meters on a Budget
There are very good reasons why you should not let this fascinating band “slip through your fingers“. The first is propagation. It typically is the last and least likely band to fail under adverse propagation conditions. It is primarily a night time band when it comes to DX due to D-Layer Absorption during the day. At that time, in particular the morning, and at night, it can provide NVIS (Near Vertical Incidence Skywave) mode propagation for local contacts. In times of local disaster when a repeater is down, this mode can get communications over mountains. 80, 60 and 40 meters can equally be used in NVIS mode propagation, depending of ionosphere conditions, but I’m only concentrating on getting you on 160.

160m-top-band-endfed-antenna-g3yeu-iss1-31.pdf
Links to a PDF file to download

Topband in Hawaii
The topband is rough in Hawaii with everyone else 2800 miles or more away. There can be significantly less thunder crashes much of the time versus the mainland. However we get fishing floats. These are believed to be illegal locator transmitters sending slow CW from top to bottom on the band. They are used by fishermen to relocate their drift nets in the Pacific ocean. They send a CW id and then some long dashes typically. The usual “Call Sign” uses three randomly letters, sometimes with a number mixed in.

Topband – 160 meters – Power Line Noise, de NØRQ
The 160 meter band, often affectionately called Topband by enthusiasts, is unique among all the amateur band allocations.  It is the lowest frequency range we can transmit on, and it presents technical challenges similar to the 80m band but in greater degree.  It is also called “the gentleman’s band”, because almost all the operators you’ll find there are good ones.  Technically, I believe that Topband is actually a MF (medium frequency) band, not HF, but those are artificial distinctions.

Top Band Magic: The Inverted L on 160M – brushbeater
JohnnyMac shows the radio world how it’s done. The ability to make and rig your own antennas is one of the cornerstones of communications preparedness- and his success demonstrates the praxis of what I teach. 160 is a big time challenge for a number of reasons- the antenna size being one- and his success at not only making solid regional QSOs but at QRP power levels on SSB no less demonstrates not only what’s possible  but how to do it on the cheap.

http://www.ok1cz.ddamtek.cz/160m_70s.html
160m is a special band. Like many fellow Topbanders I love it for its magic and challenge. I don’t feel like an old timer yet but I thought some of the memories would be of interest to those of my generation and possibly to the younger ones.

http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/pw/1991/08/page19/index.html
There’s been a lot of interest in 1.8MHz a.m. operation recently. To get you on Top Band’, the Rev. George Dobbs G3RJV and Ian Keyser G3ROO, have come up with the PW Chatterbox, a complete a.m. station.

160m – Topband – best for solar mimimum

I was digging around on the net today looking for simple deigns for Topband,  160M gear.  I found this article saying that it was best for solar minimum:  “The 160-Meter Band: An Enigma Shrouded in Mystery” which first published in CQ magazine in 1998. Here is some of what it says:

“Topband is one of the last frontiers for radio propagation enthusiasts.”

“The correlation between sunspot numbers and signal strength is only about 5% as strong as the correlation on higher frequencies.

”There are several important components that can improve your chances of successfully working DX on Topband. […] The trick here is to wait for sustained intervals of quiet conditions over the high latitude regions.”

It used to be the band for local rag chewing and I get the feeling it is either classed as just that or seen as the preserve of DX chasers with huge antennas farms. It can be both, but we can all have fun on Topband over the coming years without the constant depression of low or non-existent sunspots. I have a 38m long inverted L and had reasonable results on 160M a few years back so please do not dismiss the band without giving it a try.

It also appeals to me because it was my first intro to amateur radio. I used to look out of my bedroom window across the road to an aerial pole in the back garden of the next street. It belonged to G3LIO, Jim Gibbs. He was the first licensed amateur that I knew, and he and his father were very generous in helping me to start short wave listening back in the mid-1960s.

I have a few projects to complete to get back on the air but over the coming months I will make some Topband gear and give it a try. It will be low(ish) power AM to begin with. I also like the idea of working /P with long wire antennas supported by tall trees. It is time to modify the catapult launcher!

The antenna

The antenna is back up after 6 years! Nothing fancy just an inverted L at about 11m (~35ft) and around 38M (125ft) long. Still need to put in a counterpoise in the lawn but the ground is rock hard after weeks of drought, so it will have to wait.

Also need a remote tuner and plan on making one based on an Arduino.
https://hamprojects.wordpress.com/2016/12/31/hf-automatic-tuner/

I have a nice waterproof box that housed a commercial tuner to house it and will probably make it solar powered to avoid have to DC up the coax. Hope to get the coax in this week, it is something like a 40M run of RG-213. So, work to do before winter!

Tracking electrical storms

When a thunder storm is forecast I always disconnect and earth the antenna. Yesterday the UK Met Office  issued storm warnings for central and southern UK. A good way of tracking storms is to use an EU weather radar that gives a real time 3 hour forecast. You can pin your location making it easy to see if you are in the path of approaching weather. The storms missed this QTH, the northern edge being about 80 miles south of here.

The site is also a useful resource for predicting short term weather for portable operation. Like any weather forecasting it is not infallible!