Have you ever tried a MOXON for DXing on 87.5-108, or even used it for tx? After building one, I have made a rough comparison between that and a 3 ele. Yagi-Uda, and found both were about the same. They're still "alive", but aren't being used for ages.
My DX antenna is seldom used 8 ele. TRIAX (Danish) that had to be removed off the AR 300 XL rotator a month or so ago as this one got stuck with lots of corrosion. In sum, a cheap piece but also a very bad quality one.
Further to my 31st May last post, and in view of the developments with this RFsource stuff, I feel the obligation to explain RFsource, to whom I had sent my MF exciter+amp., has worked on the items and returned them fully interconnected. I got the tx back a few days ago.
Those who provided me some help discussed about the voltage, so now I am awaiting RFsource's comments on using either 12 or 24 so as not harm those PA FETs, meaning I won't even dare to use 12 V= to see how it goes.
So I must only praise RFsource for their assistance, and if the initial failure of contact was indeed due to what they explained after a lot of time waiting for such assistance, then my harsh words are to be ignored.
The antenna has been waiting for this RFsource tx, and has in the meantime been used with that "other", mystery tx I talked about here. Unfortunately, as I said this one doesn't send on DSB/AM, but carrier+one side band meaning audio quality does leave a lot to be desired...
As far as I know (so, others more technically minded, pse. go ahead too!), there's no need for a transformer as the angle between the vertical element - the radiator - and the artificial ground plane - the "radials" - turns the impedance value to about the same as the 50 Ohm co-axial cable.
In theory, such an antena will work w/ just one "radial", but such a configuration is not adequate, so more are used, typically a minimum of about 3.
Many days past since I posted my 9th inst. message and... "many, many replies arrived."
Not to worry, the capacitance issue was solved, and I'm now using the homemade C-L-C type ATU with something new instead of a mere inductor which is a variometer I decided to build, and if not fully correctly made, it is about enough for the present sitation.
Maybe someone could try 1675 evenings and find "something" out of ordinary in terms of the usual content in these matters, if a 30 watt signal is capable of some reach that is...
Not quite "dead." On MF, which is particularly tough to observe [Greek stns that is] here in SW Eur., I logged ERA Komotini 1404 just yesterday, 18/6, and ERA Xaniá 1512 is being heard as I write.
On HF, the fqs for R. Station Macedonia and Foni tis Elladas are relaying the same [unknown] channel since last week:
Maybe this particular topic doesn't belong here, but I would nevertheless mention it as it is related to adjusting aerials.
I found a useful table entitled "Antenna Calculations from Panaxis for MW Antennas", but there's a parameter I don't quite understand which I'll explain later.
The question is this: is the "additional capacitance (hat, etc.)" parameter supposed to be be filled with the length of the top hat (in my case, a 45 m wire) or the capacitance of it?
If it's the latter that's correct, how we determine the value?
Needless to say the aim is to determine the inductor for a given QRG used with an aerial which in the case of yours truly is a 20 m lead into a 45 m wire, or in simple terms a 20+45 inv. L.
That's the only parameter where my doubts reside.
I'd highly appreciate if someone could provide any help. Thanks in advance.
This is to let you know, that I finally got a message from RFsource days ago whereby the owner (?) explained none (!) of my earlier messages were received, only the latest one complaining for a lack of response. The "culprit", he explains, may have been an anti-virus prgr that blocked some mail... but no message was returned.
Since he agreed to check both items - the PLL exciter & the "pallet" amp. -, I mailed it today, so let's wait and see what happens.
Having said that, I have no objection *whatsoever* in withdrawing the previous comments I issued here, and if the goods are actually properly checked and returned in operation order, then, again, no objection in sjuggesting this company to others in the milieu.
Sure, the iTx, exactly like similar others, are theoretically designed to use what I term as a miserable 3 m long piece of wire as an antenna. This is pathetic.
Of course, the so called Part 15 of the FCC doesn't apply elsewhere but in the US alone, so that is *no* concern whatsoever for us in Europe, and that's often why some valuable data on txs & antennae never consider longer pieces than the ones allowed to US users.
(I notice you don't use to refer to the metric system - I take it you're somewhere on the side of the Brit. Channel, , but not "across the pond" - true?)
As to an ext. amp., oh no, I am using nothing of the sort. The one & only amp. I have is that RFsource "pallet" that got damaged, and besides that the RFsource PLL exciter to drive the former. Until at least the latter is fixed, for it vy. much seems it's faulty, I only have the iTx and that "other", mystery tx I don't use for two main reasons: a) it sends on A3H, not DSB/AM, meaning audio quality is actually worse than that of the iTx, and b) it is not meant for prolonged operation just like most (if not all) amateur transceivers. At the least the dedicated, fan cooled PSU runs hot. The tx also has a fan by the way.
You mention 10 watt, but I never said the iTx puts such power level; perhaps you're confusing with the "other" tx. This one has the following specs.:
SSB/CW 250 w PEP, A-3H 80 w carrier + sideband (upper) Duty cycle 100% for those 3 modes Tune, SSTV, RTTY, w/o fan, 33%, 5 mins. tx max., w/ fan 100%.
Finally, again on the iTx, I shall try your suggestion of bypassing the L3 coil and possibly the C8, and see what happens aerial wise. Apart from this I don't know how power could be increased a little bit on the iTx: a different oscillator valve perhaps? But then I'm convinced the voltage might be diff. too.
Oh, one other thing I forgot to add after installing the new lead: in terms of audio quality, there was a slight improvement too. I am aware modulation quality varies acc. to the diam. of the radiating element, so this must at least one of the explanations.
Well, to start with, that 25º angle I mentioned, it's wider for the time being as you cabn see it on the attached drawing I prepared. I should have explained it a bit differently, I mean the angle *will be* 25º *after* I shorten this current 17 m long lead in and leave it closer to the house, in a way I can conveniently house an ATU, viz. under the edge of the 3 m high roof on the garden opposite to the house.
About feeding the iTx or the "other" tx directly w/ the 50 Ohm cable, no, that only exists between the home made L-C-L ATU or the DRAKE MN-7 and any of the other two txs, be it the "mystery" one or the iTx.
The "mystery" tx, possibly like others covering 160 m, can, as I said, send down to 1500 (even a bit lower than that), but you know better than me the circuitry was not designed for that, hence the vy. low power level it can reach at 1620, 10 w, and not a bit under 20 as I said the other day. Of course, the power level increases as one goes higher, like 1660 where think the SWR/pwr. meter of the DRAKE MN-7 can be properly adjusted prior to measuring.
Finally, the range of the iTX. After the Sunday's changes, I checked on the Land Rover 110 radio today, and could see the range did increase as I can still hear the signal well over a km away all depending on the blockage by buildings, so I can only imagine it can be picked up at a greater distance on a house rx w/ an ext. aerial, I mean rxs like those we DXers use.
As to the tx I am using, the "complex" iTX, I am also enclosing the schematics of it where you can see there's no transistor there, it's a valve unit albeit very simply constructed. BTW, the new inductor for it now consists of 19 turns of 1 mm diam., insulated, multifilar wire around (don't laugh) a used silicone rubber container which translates into a 5x22 cm cylinder shaped tube - and it works nicely 1400~1900, so fits the fqs I use.
Kage, if you feel a new Thread is more appropriate for discussions about aerials, please do open one.
Thanks for coming back with the information & other tips.
Now that I mentioned .elektrodump.nl, some of their txs are about the same, if not the very same found in .pll.gr.
Unfortunately, some of the roller inductors depicted by the Dutch firm miss the value, e.g. www.elektrodump.nl/1659-Rolspoel.html, but I'll drop them a line as tapped coils are simply not as good & practical.
Txs from Northcountry R, Ramsey, SSTran & others like three models of 3, 10 or 25 w covering just 1350~1700 from R.Morningstar have been put into equation before deciding for (you guessed) the RFsource PLL exciter. The fact is, that ordering something from the USA (or from any non-EU countries) turns things complicated.
Having said that, of course, I read about variometers too, but haven't decided to build one. This 100 turn coil I have for iTx was made acc. to what I could read in Northcountry R.
As far as the iTx is concerned, the type of circuit is not allowing me to use this home made ATU after modifying it to work in an L-C-L arrangement. It's far better to use the inductor I built last year: 100 turns, tapped every 10 turns, over a 5 cm diam. form; I can send on *any* fq way up to at least 2 MHz. You know this tx, of course, so you know valves are a lot more forgiving in terms of mismatch. I'd like, however, to try another PA valve that might put a few more power w/o modifying the PSU ("battery eliminator") that I also bought.
The antenna. I said I couldn't have more than a 8~10 m long lead. Well, weather was a lot better today so I worked on the T2FD and also on the inv. L, and decided to hang it at the same height the upper tip of the T2FD is, 17 m above ground, and so I did it.
The 45 m inv. L lead is now reaching the garden, meanig it's abt. 17 m, but I decided to take it to the radio room and experiment with it.
Frankly, it was a bit of a disappointment! I was expecting a stronger signal on my rxs, but that is not the case. I also tried it with the "other" tx + the L-C-L ATU, and could see nothing marginal improvements as checked with SWR/power meter of the DRAKE MN-7 ATU (which was *not* used for tuning, it was used solely for measuring the signal). Maybe on account of now so good grounding but I have to work w/ what I have.
I suspect you'll now tell me to place the lead tip at ground level and put the ATU+inductor there, and then a 50 Ohm cable into the house. This is planned for the days to come.
Unfortunately, the longer lead I now have is not vertical, it slopes on a 25º angle, and is somewhat near one or the tower guy wires as well as a 450 Ohm ladder line for a 2x15 m, 60 m band inv. V.
Let's see how the next experiments go. Again, thank you for your help, Kage.
Contrary to what I expected on Friday, I was unable to modify the lead of this 45 m inv. L, but at least experimented a bit with coils with both the mini-tx (iTx) as well as the "other" tx, both via the modified ATU.
On the iTx, I removed the coil w/ taps that I had inside the tx plastic box and built a new, external coil with taps: 85 turns of 0.8 mm diam., insulated unifilar wire on a 9 cm diam. form. No ATU, just the inductor. Since my usual fq is 1593, I tested & tested... and it seems the best signal is achieved on the tap 7 (=70 turns), but, surprisingly or not (this iTx is too rustic) there's a fairly strong signal on the same fq on other taps too...
Then the "other" tx. As expected, tuning is a lot more critical, but at least the ATU works well despite being uncertain about the smaller var. capar. value, and the power level is higher of course. Fq wise, it's no surprise that the strongest signal is around 1690 because of the inv. L+lead dimensions, but I don't want this fq - too high for picking up the signal on either jeep radios.
A tapped coil is a poor, home made "roller inductor", but would like to use one instead.
Would you suggest a roller inductor w/ the value mentioned here www.elektrodump.nl/1662-Rolspoel.html for instance? Would appreciate a word from you on this.
Aerials. I know the inv. L is nothing but a variant of the traditional monopole, but either this current inv. L or a shorter inv. L, like 25 m hung somewhere else is all I can use for tx as I already have other [receiving] aerials around.
The lead cannot be longer than, what, some 8~10 m.
I wanted to come back after the mods. on the ATU, which is now an L-C-L system, meaning the inductor is to be connected between ground & the junction of both var. caps.
The experiments so far have been somewhat positive (on & around the fq I use, 1593), with just a trial coil of around 30 turns of insulated, multifilar, 3 mm diam. wire on a 11 cm diam. form. I'm using nearly 10 m of this wire I bought for the new lead of this 45 m inv. L. Tomorrow, I intend to build a new coil with taps and then see what happens. The inductor will preferably place indoors, next to the ATU.
Weather permitting (it's been late Winter time like here), tomorrow too I hope to modify the inv. L lead which, among other wrong aspects, is constantly swinging because of strong wind.
I tried all this with a DRAKE MN-7 ATU used just for measuring the SWR & the power level which may surprise you as the tiny iTx hasn't enough power to allow any readings *at all* on this network, but I used something different just to "see" how the antenna+inductor were performing.
It's something that can theoretically tx down to a bit less than 1500, but on 1620 the max. power is already low, not more than just a bit less of 20 w. The signal, buy the way, is not AM, it's A3H,, not DSB/AM.
Even before experimentating with a mini-MF tx I have already referred to elsewhere in this forum, I decided to try to see whether I could improve reception a bit.
I have two different sets, both on 2 Land Rovers:
- Disco' TD5 II Series. Grundig WKC 5300 RDS Infomat, which can tune each 1 kHz instead of jumping every 9 kHz, but the upper limit of the MF band is 1602 kHz. The antenna is a 2 element, tiltable, Bosch telescopic of abt. 1 m mounted on the roof, near the upper edge of the windscreen. I regret the limited MF coverage.
- Defender 110 SW TD5 JVC KD-S 6060, tunes LF/MF on 9 kHz steps, upper limit is 1620. The antena is a multi-element telescopic near the bonet, just close to the windscreen, close enough that I can touch it if I stick my arm outside. I simply hate the rx, but it came along with the jeep, and I didn't want to spend money on a new one.
The Disco' has a rear suspension working off compressed air and this along with other car electronics pumps some noise into the rx. Apart from that, light switches, pedal brake, etc. also make noise when activated.
The Def'110 isn't that critical, but still generates some noise.
I didn't have much to look for except inspect the co-axial braid connection & antenna base which in the case of the '110 was simply wrong from factory! The paint was still there, so the electrical connection was none. Sanding the metal beneath and screwing the antenna back solved a good portion of the problem.
However, on both sets, I decided to experiment with an Amidon toroidal core I had around, viz. the FT-140-J ("J"=075 material): pulled both radios, disconneted the antenna plug and made a few turns around the toroid. Too few is almost as nothig, too many, or as many as you can insert, is too much; I found 4-6 to be the best compromise.
Result: MF reception did improve, and so did noise. I still have it, but in a lesser extent.
Maybe a different toroid would suit this need better, but that's the largest I have around that can accomodade the diamater of the 75 Ohm co-axial cable used between either antenna & the rxs.
I believe the drawing I prepared mislead you: the sloping steel guy wire (the longest of the 3 this towr has [the remaining 2 are anchored on the roof]) is being used merely to enable me getting a vertical lead from the window up.
You may see there's a short wire going from that lead to the 45 m of [horiz.] wire which is acting like a capacitive top, or hat as Engl. speakers call them.
That's why I said the installation is far from the ideal, so it does need improvement, if not for a better tx, then at least to squeeze the max. out of the tx I am using now, a very modest two valve "iTx" set I'm sure you know about.
No, this isn't for "pir. radio", nor any tx I may use in the future will be which is why I'll be happy with modest power. In fact, the RFsource amp. we've talking about elsewhere in this forum has far more power than I'd like to use.
So, finally, what I really must do is to improve the sort of ant. tuner I have after modifying the inv. L, perhaps by placing a coil/inductor on the roof.
"When it comes to MF, unless you have something with a high radiation resistance, like an Alexanderson array, or an antenna 1/2 wave or more tall (for verticals), or a horizontal less than 1/2 wave in height, you might want to check out impedance transformer un-un's or just work with a straight tuner. These will have the best efficiency with electrically short antennas."
Dear cmradio,
As far my installation is concerned, and for now, I am using a once idle receiving only antenna consisting of a 45 m long inv. that I am still to hang at the very top of the 6 m tower adjacent to the roof instead of just at a point between its middle and the top, and then prepare a convenient lead.
From the drawing I am enclosing in this, I know the lead in is far from ideal, but I wanted to experiment. The sort of lead is a 50 Ohm cable that has the braid & the inner conductor soldered together, then goes to the house and into the antenna tuner I built.
Any comments or help will, of course, be appreciated.