eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net


Reviews Categories | Transceivers: HF Amateur (inc. HF+6M+VHF models) | ICOM IC-720A Help


Reviews Summary for ICOM IC-720A
ICOM IC-720A Reviews: 49 Average rating: 4.0/5 MSRP: $50 cents
Description: All band AM/SSB/CW HF transceiver with general coverage rx.
Product is in production.
More info: http://www.classicicom.com
Email Subscription
You are not subscribed to this review.

Subscribe!
My Subscriptions
Subscriptions Help

You can write your own review of the ICOM IC-720A.

<— Page 2 of 5 —>

IW9HGS Rating: 4/5 Mar 15, 2008 14:08 Send this review to a friend
RUGGED and fascinating! :)  Time owned: more than 12 months
I like this transceiver. Mine suffer of some little problems : the rotary switch had to be cleaned very well to become perfect, and the frequency counter is not so perfect. But is very nice and easy to use; rugged and solid!!!
 
VE3ES Rating: 3/5 Jul 24, 2007 21:00 Send this review to a friend
Old quirky ICOM  Time owned: more than 12 months
Nice vintage ICOM worthy of having in your shack. Also had the AT-500 tuner, the PS-30 power supply, the matching spkr and the matching desk mic. Probably as good as they came back in the 80s but a somewhat unique radio with this really loud relay that kicks in when switching bands. That alone ruined the rig for me. I recently sold the station and it's replacement is a much newer FT-840 which is light years ahead of the ICOM. Again, a nice vintage radio but find yourself something better like an IC-730, IC-740, IC-745, etc, or better yet anything made by Yaesu.
 
EA2FL Rating: 4/5 Nov 23, 2006 09:06 Send this review to a friend
Good Old Rig  Time owned: months
My father gave me his old 720A radio. Two problems: 1.No good RX until PTT was pressed a couple of times. 2.Attenuator was useless, 50dB signal drop. I found out that relays need to be cleaned since no DC courrent was flowing over them. I unsoldered R5 and R9 from ground and connected them to +DC, on SWR unit. Now relay auto cleans with DC, and 13dB attenuator works fine and stays ON on lower bands. S-meter readings are too generous when att is OFF.
I also had to adjust frequency reference and USB capacitor, plus LSB and CW and coils.
RX is good and TX is adjustable from 1w to 100w if compressor is ON. Only 2.3 KHz TX audio was too narrow for SSBquality required nowadays, so I added the 1.8KHz, ref123, INRAD filter. The old one stays there only for narrow CW now. Both TX and RX quality have improved. IF pass band tunning is much easier to use. Compressor makes TX audio stronger but very "thin" wich is OK for DX. When OFF, TX audio sounds so much natural!! I still have to check processor adjustment.. Let's see what I can get. Any advice over there?
Fan works everytime you transmit and was a bit noisy. So I have replaced the old fan with a new one, and much more silent one!!
Good old rig with general coverage, MW RX antenna plus only RX connectors, for an RX antenna and/or pre-amp option.
Old, but... Works Fine!!!
 
KC8HKI Rating: 4/5 Jul 3, 2006 08:04 Send this review to a friend
Great radio, Great Price!  Time owned: more than 12 months
Love the IC-720A. Mine has a few problems, But we'll get them one day.

I wanted to let you guys know about my problem - It might save a few more IC-720A's.
My 720A's rotary relay switch was never making contact with the contact pads. It'd click 20 or so times, passing the appropriate contact several times, and finally give up, stopping randomly. The detent ring on the switch was loose, so the switch contact would always land between two contact pads! When I epoxied the detent ring to the shaft (where it was loose) it worked, and now the contact lands perfectly on the pad, and has worked since. It never clicks more than 6 times (7 position switch - if it clicks 7 times, it'd end up right where it started!)

I use this radio as a backup/emergency/portable rig. Built very ruggedly, and has a wonderful feel.
I definately recommend this as a first rig, backup or portable rig!
 
RZ3DFS Rating: 5/5 Apr 3, 2006 02:28 Send this review to a friend
Solid old radio  Time owned: more than 12 months
It's a great solid constructed old radio. But it needs a maintenance in time.
See my illustrated review (russian):
http://dx.com.ru

73!
Alexander Breuss
RZ3DFS
 
AC5XP Rating: 5/5 Jul 26, 2005 11:38 Send this review to a friend
Classic early-eighties HF SSB radio from Icom  Time owned: 0 to 3 months
The Icom IC-720a HF radio
By Loek d’Hont AC5XP

The Icom IC-720a is another one of those great radios from the late seventies/early eighties. Some weeks ago I was lucky enough to buy a near-mint example of these.
In the days when this radio was sold new, I spent most of my money on Yaesu radios like the FT-757 and FT-767 which were (some of) the IC-720’s competitors of the day. It now turns out that selecting Yaesu instead might have been a mistake; I should have bought the Icom. The IC-720 is clearly a better radio than the two Yaesus mentioned; both in construction as well as performance. (See my not-so mild reviews for the FT-757 and 767 for the rest of the story!)

The IC-720 must have been one of the very first general-coverage transceivers that Icom developed, having a first IF frequency in the VHF range.
The radio is in fact a double-conversion superheterodyne radio, although in some publications it is called a quad-conversion. The reason is that the third and fourth IF are only used for the variable IF shift, where the fourth IF frequency is identical to the second; a well-known variable bandwidth concept (NOT just an IF shift!) invented by Collins, where two sharp filters "run into each other"
The radio came well-equipped with filters from the get-go: a solid (physically very large!) roofing filter in the first IF at 39.73 MHz, two crystal filters (AM and SSB) in the second IF (9.0115 MHz) and a crystal filter in the third IF (10.75) used for the variable bandwidth feature.
Optionally, an additional AM filter can be added for the third IF, and a 500 Hz CW filter for the second IF. I was lucky enough to have the CW filter already installed.
From a construction standpoint, I really like this one. It has aluminum alloy die-cast panels on the sides, back and front. The top- and bottom covers are made from very thick sheet metal, much thicker than what the competitors used. The whole radio is painted in a dark-green metallic tint, which looks almost military. The over-all styling makes the military impression even stronger.
From the inside, everything is laid-out very well, it makes for a very clean impression. The buildup is modular; practically every PCB board is in its own tin can. The same thick sheet metal is used as a frame for the modules. The interconnections are all done with high quality connectors. The PA is completely integrated in the large, diecast heatsink on the back and is equipped with a very quiet fan. The power supply is external, the radio runs of 13.8 volts DC at 20 amps peak which is kind of the norm for 100W solid-state radios for this frequency, now and then. In receive mode it draws about an amp.
The controls are all laid-out logically and feel solid, including the push-buttons. The main dial has a superb, adjustable flywheel action, one of the best I have ever experienced. The large, heavy knob feels like it tuns on ball-bearings and is completely free of any mechanical play, much better done than later Icom radios like the 746 and 756 series.

The radio uses a rotary relay as a microprocessor-controlled bandfilter selector for the transmitter filters. I have never seen this before in any ham radio, although I am very familiar with it for commercial and military radios. The stepper is quite noisy but it seems to work well. Many other IC-720 users have reported problems with this stepper relay but I haven’t found any, which might be because my radio was used only lightly by the previous owner.
If you have seen the QST report for this radio you will find that the two-tone dynamic range was tested to be over 90 dB for this radio, a significant result for a radio almost 25 years old.

Now for the bad news.

If you have to service this radio, you have a problem. The inside module cases are mounted on top of each other and very difficult to reach. And almost impossible to work on in exposed condition without an extender wiring harness.
The most difficult to reach module is the PLL unit. And this is where my radio actually had a problem; it lost PLL lock in a 100 kHz band section which repeated itself every 1 MHz. This point in the direction of a VCO having drifted out of its control range in one of the PLL sub loops (most general coverage transceivers of the pre-DDS era had this intricate system of 3 PLL loops in the frequency synthesizer)
I managed to expose the PLL module by carefully moving the two modules (RF and IF) out of the way. By doing so, it was impossible to maintain RF connection to the other modules, but this is not such a problem as long as the synthesizer still gets the control signals from the CPU, as well as the supply voltage, then it can function on its own but without the receiver being active. I actually felt like a surgeon applying a heart-lung machine to the patient…

The synthesizer concept used in this radio is different from traditional designs. It is a very novel concept where two VCOs run practically parallel, where the control voltage for the first VCO (this VCO is part of a traditional wide-band PLL) is used as a coarse control for the second (and main) VCO (which is the one that generates the actual first LO for the receiver). The second sub-loop (the one that generates the 100 Hz steps) then is used as a reference for the main VCO (and PLL) such that the actual PLL control for the main VCO has a voltage control range of only 200 kHz or so. In this way one gets the best of two worlds: Lower phase noise that traditionally can only be achieved with “narrow” PLLs, while still allowing for the full 30 MHz range for the main VCO as a whole.

But as so often, highly innovative designs can (will) suffer reliability problems in the early phases. That’s the price one pays for this concept as well. It requires a very good tracking mechanism between the two parallel VCOs; if they drift too far apart (drift as defined in free-running condition) it will drive the 100 kHz sub-loop against the Vcc rail. This is what had happened in my radio.
Matters got further complicated because the manual has a very disturbing printing error in the alignment instructions; if you follow the instructions to the letter you will not get it to work because of that. All this forced me to first thoroughly understand the circuit before I went for the adjustment, which is difficult to do when you only have the diagrams without the description (I only have the owners manual, not the service manual)

The fact that Icom had waxed all the ferrite cores solid in the oscillator coils was another problem, I first had to meticulously clean al that, without breaking the fragile cores.
FYI, wax cleans up nicely by using petroleum-based paint thinner and Q-tips. Do NOT use lacquer thinner instead, it will dissolve the polystyrene coil formers!

As a sidenote, do you know how to secure ferrite cores in their coil-formers without using wax? Cut open your wife’s elastic hair-bands (when she is not home, hi) and salvage the thin strands of elastic rubber. Then, stick a strand in the coil-former first, and THEN insert the ferrite core. It will keep the core rigidly in its place while still being adjustable. A trick I learned a long time ago from having tinkered with old German tube broadcast radios when I was a youngster!

Anyway, it all was worth the trouble. I now have a like-new IC-720a which works (and looks) like a champ – Like I have said on many occasions, I love the way those early-eighties radios look, they don’t make ‘em like that any more!

If you need the complete user- manual for this radio, including the high-resolution scans of the diagrams and board layouts, email me. I have scanned (and restored) the drawings to the point where they are better than the original. Drop me a line and I will email you a copy, through www.yousendit.com (the file is 100 MB large!)
 
KE5ASZ Rating: 5/5 Jun 28, 2005 22:47 Send this review to a friend
Very Affordable  Time owned: 6 to 12 months
I am a college student and whenever I would go looking for a potential HF rig to buy they would always be out of my price range. Finally, the IC-720A came along and I grabbed it up for $225 with shipping. This rig may not have all the bells and whistles of modern rigs, but I can pick out those weak signals with the PBT and my ears. Now I just need to get learn the code so I can talk all of you wonderful folks.
 
9W2BBB Rating: 5/5 Jun 18, 2005 20:06 Send this review to a friend
Low-noise band SW  Time owned: more than 12 months
I have a IC-720 & IC-720A, that rotary SW is very noisy.

I fond solution here :-

http://www.mods.dk/view.php?ArticleId=2968

It work fine and quiet !

 
N4DYR Rating: 5/5 Nov 25, 2004 00:32 Send this review to a friend
Still my favorite after all these years!  Time owned: more than 12 months
Despite the one major headache that I've had with this radio it's still my favorite, after 22 years of ownership. I've loved my '720A ever since I bought it new in 1982. I used it extensively in the '80s for both ham and HF utility DX'ing.

The problem cropped up in 1987, when I discovered that if I switched to the function key modes, I couldn't switch back to normal modes. I stopped using the radio, after both Icom-UK and Icom-America tried without success to fix it. I was going to throw it on the dumpster, but put it on a shelf instead.

Recently, I took it off the shelf and gave myself one last chance to fix it before I put this great rig in with the garbage. Purely by accident, I found the bad solder joint that had been causing the problem all along.

This radio sounds great on both transmit and receive. All the controls are easy to use and, unlike some more modern rigs, it's easy to learn and use nearly every function.

Unlike my IC-718 there are no memories and no DSP, but it's still a great radio for a beginning ham, or a second radio, and is the easiest radio I know to modify for MARS operation.
 
LA6NNA Rating: 5/5 Jun 16, 2004 12:14 Send this review to a friend
Workhorse  Time owned: 3 to 6 months
Really a good and stable trx.Not like the new ones with all the fancy stuff but doing ok.Good rx and really a work horse.My main and only consern now is that I have to replace the s-meter bulb....lol.Did get it re-tuned to a local radiodoctor and now its doing fine.
 
<— Page 2 of 5 —>


If you have any questions, problems, or suggestions about Reviews, please email your Reviews Manager.