Ο λόγος στασίμων 1:1 ενός κεραιοσυστήματος, δεν συνεπάγεται τον 1:1 λόγο μεταφοράς ισχύος, προς την κεραία!

Saturday, 17 July 2021

TLC for a KENPRO 7401 - 004 rotator

 I was given as an exchange a KENPRO rotator. At first it was stuck and hard to rotate but using a long screwdriver as a lever I manage to give it a couple of turns and make it sound like grinding stones!

Actually it was grinding fine particles of mud rain usually falls to Greece when in Atmosphere there is mixture of African dust and rainy clouds!

I clean it last night into my shack so I use the less flammable liquid I could use, White Spirit.

I let it soak all night and this morning using a short haired brush I clean it thoroughly and after a general apply of special grease, its like new one rotating freely. 

Photos are not great but can can easily spot the red dust on one side due probably to slight misalignment.

Friday, 7 May 2021

6m Horizontal Dipole!

6m wire horizontal dipole built the old fashion way.
On a piece of lumber! (33mm X 45mm X 400mm) 
My Create V antenna is BLR now so until I build something new with the alu tubes I left, I used the centre plate, the CMC and the coax to assembly a 6m Dipole.

After the necessary trimming each leg of the dipole antenna is 135cm. The dipole is broad to the axis of  140° - 320° and that means  that I can work Middle East-Arabian Peninsula and Central Europe-East Coast simultaneously! In THEORY!

On average is better than the Slim-Jim I am using by 6 db or so. I've just install it and I haven't made some reception tests yet. So until I'll find a way to tame the high SWR of a W8JK antenna or a design of a bidirectional Yagi, this will be my 2021 6m antenna!
cheers and 73

p.s. the dipole is elevated @approximately 9 meters ARL and 40 meters ASL.

Thursday, 5 November 2020

Restoring the Collins 180S-1

Next on the bench, a Collins 180S-1 antenna tuner found its place.
A friend of mine ask me to have a look and remove a Plexiglas plate someone had installed for some reason adding also the missing bank of 100pf capacitors.

He new nothing of its former owners, simply he wanted to be in original state rather this mistreated one.
He was wrong as it proved. The ATU wasn't mistreated but heavily vandalised.

Some one had try to make it working as Tee rather than the original Pi/L network and a lot of interconnecting wires were missing.
Easy to cut, difficult to replace and solder. 
I ordered from the Eastern Market the missing caps and load meself with tones of patience. Internet was my help the whole time with photos and useful articles.

Step by step I disassembly it by 95% being cautious not to made a bigger damage. Luckily enough there weren't  any unnecessary wholes made at the fascia or anywhere else so cosmetically it was going to fine.
And went!
It took me some time to figure what to unscrew and how in order not to make any damage and then  widen a bit the holes to pass the bolts of the new capacitor bank being different #number that the one already punched. Small stuff of great care.
Eventually everything fell in position, nothing went missing or surplus apart of a few bolts that the former owner had used for his mod. 

So another project came to a glorious end.
Enjoy the article and the photos and #staysafe
73 de sv3auw/m0lpt

Tuesday, 3 November 2020

Building a QRPGuys 40/30/20m DSB Digital Transceiver Kit

Though I haven't post something on my blog a couple of months now, that doesn't meant that I was idle.
First on the construction bench sat quoting from their site: 
"...  The QRPGuys DSB Digital Transceiver is a low cost, multiband, DSB transceiver kit, currently with three easy plug-in band modules for 40/30/20m, (additional module pcb’s available). This transceiver is an evolution compiled from various DSB and digital designs on the internet from ZL2BMI, VK3YE, AA7EE, BD6CR, and others. With help from Jim Giammanco, (N5IB) and finally Steve Weber, (KD1JV), we are offering a transceiver with an approximate output of 2.5 watts on 40m, over 1.5 watts on 30m, and over 1 watt on 20m. The receiver sensitivity was measured at .4uV (-115dBm). All the components are included for the main board (3.0″ x 3.12″) and three (40/30/20m) band modules.

The transceiver will run the popular free WSJT-X software (Windows, Linux, or macOS) that requires an accurate time synchronization program, such as Dimension 4, or many of the other free ones available. Users will need two 3.5mm stereo jumpers to your computer or tablet microphone/speaker jacks on the sound card.

The transceiver’s internal VOX circuit will switch to transmit automatically when it senses an audio output signal from the software on the pc or tablet speaker jack. The connections to the transceiver are BNC for the antenna, 3.5mm stereo jumpers to the computer audio jacks, and 12-14 VDC for the pcb mounted 2.1mm pin coaxial power jack. Approximate power consumption is about RX-15mA/TX-350mA. The total weight w/band three modules is 3oz. (85gm). The normal tools required are a soldering iron with a small tip, rosin core solder, and small side cutters. The transceiver can be built in an evening. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 3 depending on your experience. Note also below, plans for building a 3.5″ sq. x 1.0″ high compact chassis from PCB material. ..."

This certain kit is retired now replaced by the Digital Transceiver II kit which has an optional Digital VFO board so the user can choose the Tx frequency and Tx Mode to bands from 160m – 17m.
It can easily constructed in one evening and in my Scale of Difficulty is a fair 2! As long as you are familiar with PCB soldering and toroid cores winding, is a piece of cake!
You can find the old version here but the newer and better is the one I strongly suggest to construct! 
The kit I've constructed gave me 4W on 7.074MHz, 2W on 10.136MHz and 1W on 14.074MHz. Definitely not enough power to set alight the Ionosphere but more than enough to have a constant flow of qso's!
Enjoy your time and @staysafe 
73 de sv3auw/m0lpt

Friday, 22 May 2020

How much a Kilo weights?!

The homebrew 1Kw dummy Load I've made weights exactly 1.273 grams! That is tad less than 1.3grams per Watt!
It cost me £7 /8€.That is a mere Half Penny or Half Cent per Watt!
Not bad ! Not bad at all!
The actual cost was the purchase of the 4 DL chips 50Ω/250W for a Pound and a Half each from e-bay!
 I have a box full of heat sinks bought at a Junk sale night of SARC (Southgate Amateur Radio Club) and I pay also for a copper sheet of 12cm by 50cm another £1.5/2€

Two similar heat sinks MIGed together by my Brother-in-Law along with some drilling and that was it as long as mechanical it  takes!
I cut the copper sheet to dimensions(12cm by 20cm) with a Stanley knife, mark and make the thru holes and bolt the chips with the help of 8 M3 bolts applying thermo-paste at the same time!
I connected the chips in series/parallel configuration so I have two rows of 25Ω each connected in parallel for the necessary 50Ω load!

I've built it for myself so I don't think that it needs a box to look better and then my Lin. Amp. tuning is kept short with output power less than the rated 1Kw!
73 de sv3auw/m0lpt

Κατά καιρούς δημοσιεύονται κατασκευές Dummy  Loads μεγάλης ισχύος με την διαφορά όμως ότι όταν μπαίνει το κολλητήρι στην πρίζα τα Βατ γίνονται 150 ή 250, όσα ακριβώς αντέχει το ένα μόνο τσιπάκι.
Η κατασκευή είναι απλή.

Ένωσα δύο μεγάλες ψύκτρες με MIG κι αυτό για την καλύτερη θερμική μεταφορά κι επιφάνεια.
Παρέμβαλα ένα φύλο χαλκού για καλύτερη απαγωγή θερμοκρασίας μεταξύ των αντιστάσεων και την αλουμινένιας ψήκτρας και...
και συνέδεσα τις αντιστάσεις ανά δύο σε σειρά και μεταξύ των παράλληλα. 4 x 250 = 1KW!

Ακόμα κι αν δεν αντέχει για μεγάλο χρονικό διάστημα, δεν έχει σημασία διότι δεν θα εκπέμψω με το Dummy Load κι έπειτα δεν έχω τόση ισχύ!
Δεν θα το βάλω σε κουτί παρά θα βρω μόνο έναν τρόπο να στερεώσω τον SO239 κονέκτορα καλύτερα.
Το κόστος των αντιστάσεων δεν ξεπερνά τα 10€ από το e-bay κι ένα φύλο χαλκού δεν θα κοστίσει περισσότερο από 2€. Πραγματικά αξίζει να το προσπαθήσετε κι αν το κάνετε, καλή επιτυχία!